- 


A  New 

Considerable  attention  is  now  being  given  in  Paris  to  a 
new  lamp,  the  invention  of  Messrs.  B.  Delachanal  and  A. 
Mermet,  and  intended  for  photographic  and  other  purposes 
where  a  brilliant  light  is  required. 

The  media  employed  are  carbon  sulphide  and  binoxide  of 
nitrogen.  Ignition  of  binoxide  of  nitrogen  containing  vapor 
of  carbon  sulphide  produces  a  brilliant  flame  of  a  violet  blue 
tint,  peculiarly  rich  in  chemical  rays.  The  carbon  sulphide 
lamp  by  which  this  flame  is  produced  continuously  is  con- 
structed simply  of  a  flask  with  two  tubulures,  the  vesse1 
having  about  30'5  cubic  inches  capacity.  The  flask  is 
filled  with  spongy  fragments  of  coke,  or,  better,  of  dried 
pumice,  which  imbibes  the  carbon  sulphide.  Through  the 
central  tubulure  passes  a  tube  to  within  a  short  distance  of 
the  bottom;  in  the  other  mouth  or  tubulure  is  fixed  a  tube 
of  larger  dianietar,  about  7*85  inches  in  length.  Th<- 
latter  tube  is  of  glass  or  metal,  and  contains  an  arrange- 
ment acting  as  a  safety  valve  as  well  as  impeding  return  of 
the  gas  and  preventing  explosion.  Binoxide  of  nitrogen  is 
passed  by  this  tube  into  the  flask,  and  the  gaseous  mixture 
is  conducted  by  a  caoutchouc  tube  to  a  kind  of  Bunsen 
burner,  from  which  has  been  removed  the  air  port  and  the 
cone  regulating  the  supply  of  gas.  The  binoxide  of  nitro- 
gen is  produced  by  a  St.  Claire  Deville  apparatus ;  but  instead 
of  decomposing  nitric  acid  by  copper,  which  would  be  too 
expensive,  a  mixture  of  nitric  and  sulphuric  acid  is  caused 
to  act  upon  iron. 

The  flame,  which  is  about  10  inches  in  hight,  possesses 
high  photogenic  properties,  and  is  much  superior  to  the 
light  obtained  from  the  magnesium  ribbon.  The  apparatus 
is  nearly  as  portable,  the  mixed  acid  being  contained  in  one 
vessel  which  communicates  by  a  tube  with  a  vessel  contain- 
ing fragments  of  iron.  Supply  is  regulated  by  a  cock.  The 
flame  is  constant,  unlike  that  of  the  electric  light,  and  is  not 
subject  to  spontaneous  extinctions  like  the  magnesium 
lamp.  Photographs  of  human  subjects  are  obtained  in  a 
less  exposure  than  fourteen  seconds.  Photometric  tests 
show  (flame  for  flame, per  measure)  about  twice  the  power  of 
the  oxyhydrogen  light. 

The  inventors  are  studying  the  question  of  development  of 
the  green  coloring  matter  of  plants  by  means  of  this  light. 
The  experiments  are  being  made  in  M.  Dumas'  laboratory  at 
the  Central  School  of  Paris,  an  d  the  result  will  shortly  be 
pnade  public. 


CHEMICAL  AND  PHARMACEUTICAL 


MANIPULATIONS: 


A  MANUAL  OP  THE 


MECHANICAL  AND  CHEMICO-MECHANICAL  OPERATIONS 


LABORATORY. 


FOR  THE  USB  OF 


CHEMISTS,   DRUGGISTS,   MANUFACTURERS, 
TEACHERS,  AND   STUDENTS. 


aiib 


BY 


CAMPBELL   MORFIT, 

PROFESSOR  OF  ANALYTIC  AND  APPLIED  CHEMISTRY  IX  TUB  UNIVERSITY  OF  MARYLAND, 


AND 


CLARENCE  MORFIT, 

ASSISTANT  MELTER  AND  REFINER  IN  UNITED  STATES  ASSAY  OFFICE. 


FIVE   HUNDRED   AND    THIRTY-SEVEN   ILLUSTRATIONS. 


PHILADELPHIA: 

LINDSAY    AND    BLAKISTON. 

185T. 


Entered,  according  to  Act  of  Congress,  in  the  year  1856, 

BY   LINDSAY  &   BLAKISTON, 
In  the  Clerk's  Office  of  the  District  Court  for  the  Eastern  District  of  Pennsylvania. 


C.  SHERMAN'   &  SOX,   PRINTERS- 

19  St.  James  Street. 


DEDICATED 


JOHN  HENRY  ALEXANDER, 


ETC.  ETC.  ETC.! 


IN  APPRECIATION  OF 


HIS    HIGH    MORAL    WORTH 


GREAT    SCIENTIFIC    ATTAINMENTS. 


. 


PREFACE. 


To  realize  for  Chemistry  its  true  character  of  a  science — 
to  render  it  "a  system  illustrated  and  proved  by  experi- 
ment," there  is  an  indispensable  need  of  proficiency  in  those 
manual  operations  of  the  laboratory,  by  means  of  which 
chemical  changes  are  induced,  observed,  and  estimated. 
This  accomplishment  in  manipulation — this  expertness  in 
handling  and  adjusting  implements,  it  is  true,  depends  upon 
time  and  practice ;  but  although  the  student  may  riot  become 
an  adept  in  the  art  solely  from  written  instructions,  yet 
much  may  be  thus  taught  which  will  lighten  his  labors,  and 
smooth  the  way  to  the  acquisition  of  skill  and  accuracy. 

Such  is  the  object  of  the  present  work ;  and  it  has  been 
made  to  comprise  practical  lessons  upon  the  mechanical  and 
chemico-mechanical  business  of  the  chemist,  in  reference 
both  .to  the  exact  detail  of  analytic  research,  and  the  more 
extended  processes  of  pharmaceutical  science.  Explanatory 
drawings  of  important  forms  of  apparatus,  too,  have  been 
profusely  employed  to  givevgreater  intelligibility  to  the  text; 
and  while  the  authors  have  drawn  largely  from  their  own 
personal  experience,  they  have  not  neglected  to  make  avail- 
able all  the  useful  information  that  was  to  be  derived  from 
other  sources. 


viii  PREFACE. 

In  this  second  and  enlarged  edition,  there  are  many  im- 
provements upon  the  original  work.  The  old  matter  has 
been  emended,  and  much  that  is  novel  and  valuable  added  ; 
so  that  in  its  present  form  it  embraces  full  and  fresh  teach- 
ings, adapted  to  the  requirements  of  the  uninitiated,  as  well 

as  of  the  more  advanced  student. 

C.  M. 

UNIVERSITY  OF  MARYLAND,  BALTIMORE, 
October  15,  1856. 


TABLE  OF  CONTENTS. 


CHAPTER  I. 

THE    LABORATORY. 

Its  construction;  arrangement;  ventilation.    The  office;  its  furniture,   .      17 

CHAPTER  II. 

THE   BALANCE   ROOM. 

Its  arrangement;  tables  for  the  support  of  the  balances,         .        .        .28 

CHAPTER  III. 

THE   FURNACE   ROOM. 

Its  arrangement;  the  furnace;  the  sand-baths;  the  hood;  the  steam 
generator;  the  steam  jack;  steam  series;  the  still;  the  gas  chamber; 
Beindorff's  apparatus;  the  sink;  the  draining  racks;  the  cleansing 
apparatus;  the  tool  chest, "...  29 

CHAPTER  IV. 

THE   OPERATING  ROOM. 

Its  furniture ;  the  operating  table ;  the  test  rack ;  the  spirit  lamp ;  the 
gas  furnace;  the  table  sand-bath;  the  centre  table;  the  blowpipe  table: 


CONTENTS. 

the  air-pump;  the  closets;  the  bottles;  the  labels;  the  test  case;  the 
test  series;  the  cleansing  of  glassware;  the  records  of  analyses;  index 


DIVISION   OF  SUBSTANCES. 

Slicing;  crushing;  pulverization;  Coffey's  apparatus;  mortars;  tritura- 
tion;  Hewitt's  apparatus;  Goodal's  grinding  machine;  porphyrization ; 
sifting;  sieves;  Harris's  sieve;  levigation;  elutriation;  granulation; 
division  by  chemical  means;  by  intermedia,  .....  86 

CHAPTER  V. 

THE     BALANCE. 

Its  requisite  conditions;  the  Mint  balance ;  Eater's  and  Robinson's  ba- 
lance; Berlin  balance;  Tralle's  beam;  Beranger's  platform  balance; 
preservation  of  balances,  .  .  .  .  .  •  •  •  .100 

CHAPTER  VI. 

THE  WEIGHTS. 

Metrical  or  decimal  weights;  table  of  their  relative  value  with  troy  and  • 
avoirdupois  weights ;  adjustment,  preservation,  and  handling  of  weights,     1 IG 

CHAPTER  VII. 

WEIGHING. 

Preliminary  remarks;  weighing  of  solids;  of  corrosive  substances:  of 
liquids;  weighing  of  gases;  correction  of  gases  for  moisture,  .  .  120 

CHAPTER  VIII. 

DETERMINATION   OF   SPECIFIC   GRAVITY. 

Specific  gravity  of  solids;  by  means  of  the  balance;  by  means  of  the  stop- 
pered flask;  by  the  areometer;  by  Alexander's  method;  specific  gra- 
vity of  fluids;  by  means  of  the  flask;  specific  gravity  bottles;  by  the 
hydrometer;  by  Harris's  method;  Nicholson's  gravimeter;  specific 
gravity  of  gases;  rules  for  determining  the  changes  in  the  bulk  of  gases 
induced  by  pressure  and  temperature;  specific  gravity  of  vapors;  table 
of  specific  gravities, 129 


CONTENTS.  XI 

CHAPTER  IX. 

MEASURES  AND   MEASURING. 

Measuring  of  fluids;  graduates;  the  graduation  of  vessels;  of  tubes;  mea- 
surement of  gases;  pipettes;  dropping-tubes,  .  .  ".'  "'•  .  194 

CHAPTER  X. 

MEASUREMENT   OF   TEMPERATURE. 

Pyrometers;  thermometers;  Fahrenheit's,  Celsius's,  and  Reaumur's 
scales;  rules  for  translating  the  degrees  of  one  into  those  of  the  others; 
differential  thermometers;  the  therm ometrograph;  the  mode  of  using 
thermometers;  table  of  thermometrical  equivalents,  ....  205 

CHAPTER  XL 

SOURCES  AND   MANAGEMENT   OF   HEAT. 

Furnaces;  wind  furnace;  universal  furnace;  portable  furnace;  evapo- 
rating, calcining,  reverberatory,  blast,  assay,  or  cupel  furnaces;  Bar- 
ren's wind  furnace ;  Liebig's  furnace ;  the  management  of  furnaces ; 
their  furniture.  Lamps;  glass  spirit  lamp;  heating  of  tubes  by  lamps; 
Berzelius's  spirit  lamp;  supports;  crucible  jacket;  Luhme's  and  Rose's 
lamps;  the  Russia  lamp;  Deville's  blast  lamp;  Nunn's  blast  lamp; 
the  table  gas  lamp;  the  use  of  gas  and  its  manufacture  from  grease 
and  resin;  crucibles  heated  over  blowpipe  flame;  Beale's  gas  furnace; 
Hoffman's  gas  furnace;  Hart's  gas  furnace ;  Hare's  compound  blow- 
pipe; Tate's  blowpipe;  Sonnenschein's  blowpipe;  generation  of  oxygen 
and  hydrogen  gases;  self-regulating  gas  reservoir;  the  Drummond 
light.  Supports;  the  universal  support;  wooden  supports;  retort 
holders;  tube  and  bulb  rests ;  filter  stands;  the  test  rack,  .  .  .  218 

CHAPTER  XII. 

BATHS. 

Their  construction;  the  steam-bath;  the  water-bath ;  saline  baths;  table 
of  the  boiling-points  of  saturated  solutions;  metallic  baths;  oil-baths; 
the  sand-bath, .....  264 


Xii  CONTENTS. 

CHAPTER  XIII. 

THE  MODE  OF  PRODUCING  LOW  TEMPERATURES. 

Freezing  mixtures  j  their  modes  of  application ;  ice-box ;  tables  of  the 
composition  of  a  number,  and  of  the  degrees  of  cold  which  they  pro- 
duce,   •  271 

CHAPTER  XIV. 

FUSION. 

Igneous  and  aqueous  fusion;  crucibles, — clay,  Hessian,  London,  French, 
black  lead;  blue  pots;  porcelain  and  metallic  crucibles;  iron,  silver, 
platinum  crucibles;  instructions  as  to  the  proper  manner  of  using  pla- 
tinum crucibles ;  directions  for  heating  crucibles ;  fusion  of  substances 
unalterable  by  heat  or  air;  of  substances  alterable  by  heat;  of  bodies 
alterable  by  air;  of  difficultly  fusible  substances,  .  277 

CHAPTER  XV. 

IGNITION. 

Ignition  of  filters;  of  bodies  in  vapors;  with  fluxes;  non-metallic  fluxes; 
metallic  fluxes;  fluxing  and  calcination;  coking;  incineration;  roast- 
ing; deflagration;  decrepitation;  reduction;  reduction  by  charcoal; 
by  hydrogen ;  flexible  tubes ;  india  rubber  gas  bags ;  reduction  by  car- 
bonic oxide;  roasting  and  reduction  in  tubes;  combustion  in  glass 
tubes;  tube  jacket;  glass,  porcelain,  metallic  tubes,  .  .  .  .287 

CHAPTER  XVI. 

CUPELLATION. 

Cupels;  their  manufacture;  process  of  cupellation;  muffles,— Taylor's,  .     310 

CHAPTER  XVII. 

SUBLIMATION.— DISTILLATION. 

Sublimation;  in  tubes;  in  flasks;  in  retorts;  in  alembics;  in  crucibles; 
in  shallow  vessels;  Ure's  apparatus;  hydro-sublimation.  Distillation; 
the  still;  the  cooler;  Gedda's  condenser;  distillation  in  retorts;  the 


CONTENTS.  Xlll 

mode  of  arranging  apparatus  for  distillation ;  receivers ;  distillation  in 
tubes;  platinum,  iron,  porcelain,  earthenware  and  stone  retorts;  gene- 
ral rules  for  distillation ;  of  liquids ;  of  volatile  liquids ;  application  of 
freezing  mixtures;  Florentine  receivers;  cohobation;  rectification; 
distillation  of  gases ;  tube  apparatus;  flask  generators;  funnel  tubes; 
Kemp's  generator;  Fresenius's  sulphuretted  hydrogen  apparatus ;  col- 
lection of  gases;  solution  of  gases;  WolfFe's  bottles;  safety  tubes; 
gasometer;  caoutchouc  bags;  gases  received  in  Pepy's  and  other 
gasometers;  transferred  from  gasometers;  mercurial  gasometer;  De- 
ville's  gasometer ;  pneumatic  troughs ;  the  water  trough ;  bell  glasses ; 
gas  jars;  the  mercury  trough ;  gases  collected  over  air;  transfer  of 
gases;  distillation  in  vacuo;  dry  distillation;  heating  under  pressure 
in  tubes,  V,  •»•-•"•  .  .  .  .  x  .  .  .  .  .  314 

CHAPTER  XVIII. 

LUTES. 
Lutes  for  coating  fire  vessels;  mode  of  applying  lutes,   ....    380 

CHAPTER  XIX. 

THE   BAROMETER. 

Its  principle  and  application ;  stationary  and  portable  or  mountain  baro- 
meters; wheel  barometer;  cistern  barometers ;  Newman's,  Troughton's, 
Fortin's,  Hassler's,  and  Alexander's  barometers ;  Gay  Lussac's  syphon 
barometer;  Morland's  diagonal  barometer;  rectangular  barometer; 
Daniell's  water  barometer;  sulphuric  acid  barometer;  Adie's  sympie- 
someter;  aneroid  barometers;  Bourdon's  barometer;  Wollaston's  and 
Regnault's  barometer;  register  barometer;  table  of  corrections  for 
capillary  depression  in  barometer  tubes;  table  of  barometric  correc- 
tions for  temperature,  Vv  n,:  •: 336 

CHAPTER  XX. 

SOLUTION. 

Solution, — simple  and  chemico-mechanical ;  neutralization;  solution  of . 
solids;  of  liquids;  of  gases;  table  of  the  solubility  of  salts.      .         .417 

CHAPTER  XXL 

MACERATION. — INFUSION. — DECOCTION. — DIGESTION. 

Digestion  under  pressure ;  Papin's  digester ;  D'Arcet's  and  Mohr's  di- 
gesters ;  boiling  in  tubes ;  test-tubes ;  beaker-glasses ;  flasks  and  cap- 


XIV 


CONTENTS. 


sales-,  solution  by  steam;  by  displacement;  Robiquet's  displacing 
apparatus ;  by  Cadet's  method ;  under  pressure  by  steam ;  Duvoir's 
apparatus ;  pressing,  •  '•'- v  •  :  •" '  t 437 


CHAPTER  XXII. 

EVAPORATION. 

Evaporating  vessels;  spontaneous  evaporation;  evaporation  in  vacuo ; 
by  heat  in  open  air ;  over  baths  ;  by  steam  ;  by  heated  air ;  over  the 
naked  fire  ;  Marcet's  experiments, 463 

CHAPTER  XXIII. 

CRYSTALLIZATION. 

Crystallization  by  fusion  ;  by  sublimation  ;  from  solution ;  granulation  ; 
purification  of  crystals ;  crystallization  by  chemical  reaction,  .  .472 

CHAPTER  XXIV. 

DESICCATION. 

Desiccation  of  solids  ;  efflorescence  ;  desiccation  in  air-chambers  ;  over 
baths;  of  easily  alterable  substances ;  in  vacuo;  of  liquids;  of  gases; 
Kemp's  thermostat,  ..........  478 , 


CHAPTER  XXV. 

PRECIPITATION. 
Precipitating  vessels ;  directions  for  precipitating,          .        .        .        .491 

*  ' 

CHAPTER  XXVI. 

DECANTATION — FILTRATION. 

Decantation  by  pouring ;  by  syphons  ;  Coffee's  syphon ;  filtration  through 
paper;  filtering  papers;  funnels;  filters  folded  and  introduced  into 
funnels  ;  supports  for  funnels  ;  directions  for  filtering ;  pouring ;  spritz 
bottle ;  filtration  promoted  by  warmth ;  filter  baths  ;  filtration  through 
cloths ;  through  pulverulent  matter ;  of  volatile  liquids ;  Donovan's 
and  Riouffe's  filters,  ....  493 


CONTENTS.  XV 

CHAPTER  XXVII. 

WASHING. 

Washing  of  precipitates ;  the  spritz  or  washing  bottle ;  edulcoration  ; 
Cook's  apparatus  for  washing  with  volatile  liquids,  .  .  .  .513 

CHAPTER  XXVIIL 

THE   PRACTICAL    RELATIONS   OF   ELECTRICITY. 

Cylinder  and  plate  electrical  machines  ;  Leyden  jar ;  electrical  battery ; 
discharger ;  the  electrophorus :  Detection  and  measurement  of  Elec- 
tricity: Electroscopes;  Henly's  quadrant  electrometer;  Bennet's 
electrometer ;  voltaic  pile  electroscope ;  Coulomb's  torsion  balance  ; 
Lane's  discharging  electrometer ;  calorific  electrometer ;  the  galvano- 
meter ;  astatic  galvanometer ;  differential  galvanometer ;  Weygandt's 
galvanometer.  Application  of  Electricity :  Eudiometry ;  Ure's  eudio- 
meter. Electricity  developed  by  galvanic  action:  Wollaston's,  Daniell's, 
Smee's,  Grove's,  and  Bunsen's  batteries;  connection  of  batteries;  elec- 
trolysis ;  production  of  heat  and  light  by  galvanism  ;  Hare's  sliding 
rod  eudiometer  and  calorimotor.  Electro-Metallurgy:  Preliminary 
manipulations;  moulds;  plating  solutions,  .  .  .  .  .519 

CHAPTER  XXIX. 

BLOWPIPE    MANIPULATIONS. 

Use  and  construction  of  blowpipes;  Gahn's,  Mitscherlich's,  and  De  Luca's 
blowpipes;  economical  blowpipe;  the  combustible;  blowpipe  lamp 
and  appliances  ;  flame  ;  the  mode  of  holding  the  blowpipe  ;  the  blast ; 
the -supports ;  detection  of  volatile  substances  by  means  of  the  blow- 
pipe ;  instruments  used  in  analysis  by  the  blowpipe  ;  reagents  ;  blow- 
pipe table ;  Herapath's  table  for  testing  by  the  blowpipe,  .  .  .572 

CHAPTER  XXX. 

GLASS   BLOWING. 

Blowpipe  table  and  lamp :  implements ;  cutting  of  glass  ;  tubes  cement- 
ed, bent,  drawn  out,  and  closed ;  lateral  attachments ;  bulbs  blown  ; 
Welters  and  funnel-tubes  fashioned,  .  ...  .  i  .  G01 


XVI  CONTENTS. 

CHAPTER  XXXI. 

CORKS. 

Corks  softened,  perforated ;  cork-borer,  .        .        .        .        .         ,612 

CHAPTER  XXXII. 

WEIGHTS  AND   MEASURES. 
Corresponding  values  of  French  and  English  weights  and  measures,       „    614 


CHEMICAL  AND  PHARMACEUTICAL 
MANIPULATIONS. 


CHAPTER  I. 

THE    LABORATORY. 

THE  Laboratory  is  emphatically  the  workshop  of  the  chemical 
operative ;  and  chemical  manipulation  may  be  termed  the  practice 
of  the  science.  A  convenient  arrangement  of  the  first  is  no  less 
desirable,  for  the  success  of  operations,  than  a  proficiency  and 
skill  in  the  latter  are  indispensable.  New  facts  in  science  are 
mainly  developed  by  experiment ;  and  as  chemistry  is  a  purely 
experimental  science,  in  every  course  of  research, — as  well  in  the 
most  ordinary  experiments  as  in  the  more  delicate  manipulations 
of  analysis, — the  surest  basis  of  exact  deductions  is  a  skilful 
manipulation  coupled  with  correct  reasoning.  This  exemplifica- 
tion, by  the  hands,  of  the  conceptions  of  the  mind,  is,  therefore, 
an  art  of  the  highest  importance  in  the  study  of  chemistry. 

The  laboratory  should  be  appropriately  fitted,  and  arranged 
with  a  view  to  the  ready  prosecution  of  chemical  investigation  in 
all  its  several  branches  ;  and  being  the  place  where  most  of  the 
operator's  time  is  so  profitably  and  pleasantly  employed,  no  little 
regard,  in  its  appointments,  should  also  be  given  to  personal 
comfort  and  convenience. 

The  apparatus  must  be  selected  with  careful  discrimination,  so 
that  the  stock  may  consist,  chiefly,  of  such  pieces  as  admit  of 
being  adapted  to  the  greatest  variety  of  uses ;  and  it  will  prove, 
ultimately,  most  economical  to  prefer  those  of  the  best  materials 
and  workmanship,  though  their  first  cost  may  be  a  little  higher 
than  that  of  inferior  and  less  durable  articles.  Ample  facilities, 
to  this  end,  are  presented  by  the  extensive  assortments  of  esta- 
blishments whose  speciality  is  the  sale  of  chemical  wares  and 

2 


18          THE  LABORATORY — ITS  CONSTRUCTION. 

pure  chemicals.  They  are  now  to  be  found  in  all  our  principal 
cities  and  towns,  having  risen  during  the  last  few  years  in  obedi- 
ence to  the  requirements  of  a  prevailing  taste  for  chemical 
pursuits.  The  implements  which  they  offer,  being  skilfully  con- 
structed upon  correct  principles,  promote  the  spirit  and  progress 
of  experiment  and  facilitate  a  promptness  and  accuracy  of  results 
which  might  not  be  obtainable  by  less  favorable  means,  except  at 
a  large  expenditure  of  time  and  patience.  Moreover,  a  familiarity 
with  the  use  of  good  tools  begets  habits  of  precision  which  soon 
render  the  operator  an  adept  in  manipulation,  and  enable  him  to 
meet  the  exigencies  of  any  new  case  by  the  suggestions  of  his 
experience  and  genius. 

It  is  true  that  the  dealers'  exorbitant  prices  for  apparatus  are 
unreasonably  high,  and  in  a  measure  restrict  the  study  of  che- 
mistry ;  but  this  imposture  will  be  regulated  by  competition,  as 
time  increases  the  demand ;  for  the  original  manufacturing  cost 
is  only  a  small  moiety  of  the  retail  charge.  Even  at  present 
prices,  it  is  perhaps  more  judicious  to  draw  supplies  from  such 
sources,  for  there  is  very  little  satisfaction  and  much  loss  of  time 
that  might  be  more  profitably  applied,  in  the  employment  of 
crude  contrivances.  In  discouraging  "home  manufactures"  in 
this  connection,  therefore,  we  cannot  incur  the  reproach  of  ex- 
travagance, as  our  advice  is  based  upon  personal  experience, 
and  intended  to  protect  the  interest  of  the  student. 

In  developing  the  plan  for  a  Laboratory,  we  shall  make  our 
suggestions  consistent  with  true  economy ;  and  while  presenting  a 
design,  complete  in  all  its  details,  will  accompany  it  with  such 
incidental  instruction,  as  will  render  it  capable  of  being  modified 
according  to  the  means  of  the  operator  or  the  purposes  for  which 
it  may  be  intended, — whether  as  a  Laboratory  for  public  instruc- 
tion or  for  private  research. 

Health  and  comfort  demand  free  light,  regular  warmth,  and 
ample  ventilation  in  all  the  apartments  of  a  Laboratory.  Light 
should  be  admitted  through  side  windows,  as  they  afford  the 
greatest  advantage  for  examining  the  action  of  reagents,  par- 
ticularly in  those  instances  of  delicate  testing  which  result  only 
in  light  flocculse,  faint  cloudiness,  slight  change  of  color,  or  other 
behavior  requiring  nice  scrutiny.  By  elongating  the  sash  to 
nearly  the  whole  height  of  the  ceiling,  the  solar  rays  may  be 


THE  LABORATORY — ITS  CONSTRUCTION. 


19 


Fig.  1. 


brought  under  management  when  their  aid  is  required  in  certain 
operations. 

The  sash  should  he  hung  with  counterpoise  weights,  so  as  to 
give  facility  in  raising  or  lowering  them  for  the  admission  of  air 
or  other  purposes. 

Skylights  are  objectionable  on  account  of  their  liability  to 
frequent  damage  by  storm  and  acci- 
dent.   They  moreover  present  recepta- 
cles for  dust  and  cobwebs. 

The  warming  of  the  apartments  may 
be  best  accomplished  by  means  of  Tas- 
ker's  or  other  self-regulating  water- 
furnace  (Journal  Frank.  Instit.  xxix, 
417).  The  heat  is  radiated  directly 
from  the  surface  of  iron  pipes,  dis- 
tributed throughout  the  building  and 
connecting  with  the  generator  in  the 
cellar,  which  should  supply  them  with 
a  continuous  current  of  steam. 

This  mode  of  heating  combines 
economy  with  efficiency  and  is  promo- 
tive  of  health,  comfort,  convenience, 
and  safety  from  accident  by  fire ;  as  it 
produces  none  of  the  usual  disagreea- 
bility  of  dust  and  irregular  tempera- 
ture incident  to  "hot-air  furnaces" 
and  open  fires. 

As  the  internal  atmosphere  of  the 
Laboratory  is  being  constantly  vitiated 
by  noxious  emanations  from  substances 
under  process,  as  well  as  by  respira- 
tion, efficient  means  must  be  adopted 
for  displacing  the  foul  air  by  introdu- 
cing, simultaneously,  pure  fresh  air 
in  such  a  manner  as  to  prevent  dis- 
comfort from  cold  draughts.  The 
tendency  of  the  foul  air,  even  when  not  specifically  lighter  than 
the  surrounding  air,  is  to  ascend,  owing  to  its  being  rarefied  by 
the  heat  of  the  Laboratory,  and  therefore  it  may  be  readily  made 


20          THE  LABORATORY — ITS  CONSTRUCTION. 

to  pass  from  the  apartment  through  a  panel  of  coarse  wire  grating 
(Fig.  1,  a)  placed  in  the  wall  of  the  chimney  flue,  near  the  ceiling. 
This  panel  should  be  twelve  inches  broad  and  nine  inches  high 
for  a  room  of  forty  feet  square,  and  proportionally  smaller  for 
one  of  lesser  dimensions ;  and  to  prevent  the  entrance  of  smoke 
in  gusty  weather,  there  should  be  affixed  to  the  inside  a  hinged 
flap  (b)  made  of  very  fine  wire  gauze.  The  draught  action  of 
the  warm  flue  carries  away  the  unwholesome  air,  as  shown  by  the 
arrows ;  and  the  pure  air  entering,  to  supply  its  place,  through 
the  many  crevices  in  the  doors  and  windows,  and  about  the  build- 
ing, quickly  diffuses  itself  and  thus  becomes  warm  without  cre- 
ating any  perceptible  cold  currents.  Even  in  summer,  or  when 
there  is  no  fire  on  the  hearth  to  dilate  the  air  in  the  flue,  the  wind 
blowing  across  the  top  of  the  chimney  produces  a  partial  vacuum 
at  the  mouth,  towards  which  the  upper  air  of  the  room  will  be 
moved  by  the  upward  pressure  of  the  denser  lower  strata. 

Dr.  Murray  uses  a  funnel-mouthed  tube  instead  of  a  grating, 
and  conveys  the  tube  through  the  ceiling  into  a  chimney,  where 
there  is  a  constant  fire.  To  provide  against  the  entrance  of 
smoke  through  any  imperfection  of  draught,  the  pipe  is  continued 
to  the  top  of  the  chimney.  The  warmth  of  the  chimney  rarefies 
the  air  within  the  pipe,  and  ventilation  is  effected,  upon  the  prin- 
ciple above-mentioned. 

The  laboratory  apartment  should  be  sufficiently  spacious  to 
afford  a  separate  place  for  each  of  the  requisite  utensils.  Too 
much  crowding  of  apparatus  is  apt  to  produce  damage,  and  is, 
besides,  inconvenient ;  for  nowhere  than  in  a  Laboratory  is  there 
more  necessity  of  a  strict  observance  of  the  rule,  "  a  place  for 
everything,  and  everything  in  its  place."  Hunting  up  mislaid 
apparatus  consumes  time,  and  the  delay  thus  occasioned,  in  many 
instances,  may  be  the  means  of  serious  detriment  to  important 
operations. 

A  roomy  apartment  on  the  first  floor  of  a  building  is  best 
suited  for  laboratory  purposes.  The  first  floor  is  recommended, 
because  of  its  greater  convenience  for  the  admission  of  water, 
fuel,  &c.,  and  for  the  removal  of  the  slops,  sweepings,  &c.  It 
should  be  partitioned  off  into  four  several  apartments,  the  middle 
or  larger  of  which  should  be  the  main  operating  room,  whilst  the 
smaller  at  either  of  its  sides  are  used,  the  one  as  an  office,  the 


THE   LABORATORY — ITS    CONSTRUCTION. 


21 


other  as  the  furnace  room,  and  the  third  for  the  balances.  This 
arrangement  protects  the  middle  room  from  the  dirt  and  dust  of 
the  coarser  furnace  operations,  and  the  balances  from  the  influ- 
ence of  corrosive  vapors ;  and  what  is  equally  indispensable,  by 
means  of  the  office  as  a  reception  room,  presents  a  bar  to  all  un- 
welcome intrusion  from  without. 

As,  in  some  instances,  it  may  be  convenient  to  construct  a 
building  especially  for  a  laboratory,  we  present  the  plan  of  a 
properly  furnished  one,  such  as  might  be  completed  for  a  very 
moderate  outlay.  It  is  of  coarse  brick,  and  rough-cast  with 
mastic,  which,  becoming  indurated  in  a  short  time,  serves  as  a 

Fig.  2. 


perfect  protection  to  the  walls  against  all  dampness,  and  imparts 
a  stone-like  appearance  to  the  building.  A  very  good  mastic 
may  be  made  by  oven-drying  a  mixture  of  the  following  powders, 
and  then  working  it,  in  the  usual  manner  of  mortar,  with  one- 
seventh  of  its  total  weight  of  linseed-oil : — 14  volumes  of  sili- 
cious  sand  ;  14  volumes  of  powdered  limestone ;  1-14  in  weight 
of  litharge, — that  is,  one-fourteenth  of  the  joint  weight  of  the 


22          THE  LABORATORY — ITS  CONSTRUCTION. 

sand  and  stone.  The  surfaces,  which  are  to  be  covered  with 
this  mastic,  must  first  be  washed  over  with  linseed-oil  containing 
five  to  ten  per  cent,  of  rosin-oil.  The  linseed-oil  used  in  the 
mixture  might  also  contain  a  portion  of  rosin-oil,  which,  without 
detracting  from  its  quality,  will  lessen  the  cost  of  the  mastic. 

Figure  2  gives  the  front  view  of  the  building.  Though  regard 
is  had  more  particularly  to  economy  and  convenience  in  its  con- 
struction and  arrangement,  yet  there  is  sufficient  reservation  of 
architectural  symmetry  to  impart  a  neat  and  becoming  appear- 
ance. In  the  arrangement  of  the  ground  plan,  we  observe  the 
same  positions  as  are  recommended  in  the  adaptation  of  a  room 
to  laboratory  purposes,  so  that  our  suggestions  are  equally  ap- 
plicable to  either  case.  The  whole  front  of  the  building  is  forty 
feet.  Its  depth  is  twenty-four  feet.  The  ceiling  should  be  high, 
say  from  eighteen  to  twenty  feet.  The  roof  is  square,  slightly 
inclined,  and  of  metal.  There  are  two  entrances  only,  one  in 
the  left  wing  or  furnace  room,  for  the  ingress  and  egress  of 
material  and  refuse,  and  the  other  in  the  office  or  anteroom.  The 
centre  or  operating  apartments  are  thus  preserved  from  all  in- 
convenience of  dirt,  dust,  or  intrusion.  There  are  two  chimneys, 
that  in  the  office  being  for  the  stove-pipe,  when  a  stove  is  to  be 
used  for  warming,  and  the  other  in  the  left  wing  for  the  flues  of 
the  furnaces,  still,  &c.  The  windows  should  extend  nearly  to 
the  top  of  the  ceiling.  In  the  preceding  figure,  they  are  twelve 
feet  by  two  feet  eight  inches,  in  the  centre  apartment,  and  twelve 
feet  by  two  feet  in  the  wings.  The  glass  panes  of  the  former 
number  eighteen,  those  of  the  latter  twelve.  The  doors  have  a 
width  of  two  feet  nine  inches,  and  height  of  seven  feet ;  and 
each  should  be  furnished  with  a  spring.  Oiled  linen  makes  an 
excellent  curtain  for  protection  against  the  summer  sun,  without 
too  much  obstruction  of  the  light.  It  should  be  hung  on  Putnam's 

Fig.  3. 


"  balance  spring-rollers"— Fig.  3— in  which  the  use  of  cords  is 
dispensed  with,  the  curtain  being  raised,  lowered,  or  held  in  a 
fixed  position  by  means  of  a  counterpoise  weight. 

Curtains  thus  hung  were  exhibited  at  the  last  Annual  Fair 


THE  LABORATORY — ITS  CONSTRUCTION. 


23 


Fig.  4. 


of  the  Maryland  Institute,  by  Baker  and  Cushman,  of  Balti- 
more. The  roller  is  a  hollow  tin  cylinder,  1 J  inches  diameter, 
and  revolving  upon  a  metal  rod,  which  is  wrapped  with  a  spiral 
spring  of  brass  wire ;  and  the  combination  is  so  adjusted,  that 
when  the  weight,  disguised  as  a  tassel,  receives  a  slight  upward 
motion  from  the  hand,  the  wire  spring  recoils,  and  the  curtain  J, 
Fig.  4,  fastened  in  a  groove,  is  wound  up  by  the  roller  to  any 
desired  height.  The  roller  and  curtain  are  suspended  by  brack- 
ets at  the  top  of  the  window  ;  and  the  act  of  drawing  down  the 
curtain  turns  the  cylinder  and 
winds  up  the  spring.  This  ar- 
rangement admits  also  of  the  ap- 
plication of  a  self-acting  dust- 
bar  a,  which  consists  of  mosquito- 
netting  so  fixed  to  the  lower  half 
of  the  sash,  that  when  the  lat- 
ter is  raised  it  draws  up  the  for- 
mer to  take  its  place.  £his  ap- 
paratus will  be  found  very  con- 
venient in  windy  and  dusty 
weather,  when  it  is  desirable  to 
have  free  access  for  air  to  the 
apartment  without  endangering 
the  comfort  of  the  occupant  or 
the  safety  of  the  apparatus,  &c. 
The  roller  is  equally  advantage- 
ous for  hanging  diagrams  as  curtains. 

The  top  moulding  of  the  building  is  of  wood,  plain  and  painted, 
and  the  pillars  represented  in  the  cut,  are  only  projections  of 
the  brickwork  to  ornament  the  front  of  the  building.  It  is  seen 
by  Fig.  5,  which  represents  a  back  view  of  the  laboratory,  that 
the  rear  windows  differ  in  form  and  position  from  those  in  the 
front.  The  reasons  will  be  obvious  on  explanation.  For  the 
convenient  arrangement  of  apparatus,  it  is  necessary  to  have  as 
much  wall-room,  interiorly,  as  possible ;  and  as  the  ample  win- 
dows in  the  front  will  furnish  most  of  the  requisite  light,  the  rear 
windows,  which  are  of  sufficient  extent  to  supply  the  remainder, 
are  elevated  so  as  not  to  interfere  with  the  tables,  shelving,  and 
fixtures,  resting  against  the  wall  beneath'.  These  windows  should 


24 


THE   LABORATORY — ITS   ARRANGEMENT. 


be  hung  upon  metal  pivots,  so  that  they  may  be  readily  opened 
or  shut  at  will.     The  front  window-sash,  for  reasons  before  given, 


Fig.  5. 


should  be  counterpoised  by  balance  weights.  The  dimensions  of 
the  rear  windows  in  the  wings  are  six  by  three  feet,  and  the 
number  of  glass  panes  in  each  window  are  eight.  The  side 
light  is  also  admitted  through  three  elevated  windows  in  each 
end  of  the  building.  Their  size  is  six  by  three  feet,  with 
eight  panes  of  glass  each.  The  centre  apartment  has  also  two 
elevated  windows  in  the  rear,  but  their  width  is  one  foot  greater 
than  those  in  the  wings.  All  of  these  elevated  windows  should 
be  hung  upon  metal  pivots.  This  elevation  of  windows  in  these 
apartments  is  also  with  a  view  to  the  economy  of  wall  space 
within.  The  basement,  which,  by  a  little  expense,  may  be  ap- 
propriately fitted  for  the  purpose,  serves  as  a  receptacle  for  fuel, 
bricks,  charcoal,  tile,  rough  materials,  and  cumbersome  apparatus 
not  in  constant  use.  The  best  color  for  the  woodwork  is  white 
— preferably,  of  pure  zinc  white  ;  and  the  walls  and  partitions 
of  lath  and  plaster  should  be  smooth,  so  that  the  laboratory  may 
be  as  free  as  possible  from  loopholes  for  the  accumulation  of 
dust.  A  stiff  brush  mat  and  scraper  should  always  be  furnished 
for  each  entrance.  If  the  means  of  the  owner  will  permit  the 
expense,  it  would  add  much  to  the  appearance  of  his  place  to  sur- 


THE  OFFICE — THE  MINERAL  CASE.  25 

round  it  with  a  garden  plat.  Thus,  in  improving  the  beauty  of 
the  spot,  he  would  be  providing  the  means  of  pursuing  investiga- 
tion practically,  to  a  limited  extent,  in  agricultural  chemistry. 

Plate  2  represents  a  ground  plan  of  an  experimental  and 
analytical  laboratory,  either  as  especially  constructed  for  the 
purpose,  or  from  any  room  of  adequate  dimensions.  The  main 
divisions  of  the  apartment,  as  before  said,  are  three,  the  fourth 
in  the  plan  being  only  a  subdivision.  The  two  wings  A  and  B, 
of  equal  size,  are  10-3  by  22-6  feet  in  the.  clear.  That  on  the 
right  should  be  used  as  the  office  and  balance  room,  the  left  wing 
being  occupied  exclusively  for  furnace  and  grosser  operations, 
leaving  the  centre  or  operating  room  C,  occupying  the  whole 
residual  space  of  the  floor,  for  the  nicer  manipulations. 

The  Office. — This  being  the  studio  of  the  operative  should 
contain  both  the  library  and  the  mineralogical,  geological,  and 
technical  cabinets.  These  latter,  not,  however,  necessarily 
extensive,  are  very  convenient  for  reference,  as  instances  fre- 
quently occur,  in  the  course  of  practice,  requiring  a  comparison 
of  specimens.  The  two  front  windows,  together  with  the  two 
elevated  windows  at  the  outer  side,  serve  for  the  free  admission 
of  light.  This  being  also  used  as  the  reception  room,  there  is 
an  entrance  door,  between  the  two  windows,  of  dimensions  equal 
to  those  of  the  door  in  the  furnace  room.  The  floor  should  be 
carpeted,  or,  preferably,  covered  with  oil-cloth,  which  is  more 
durable,  and  readily  cleansed.  The  bare  spots  on  the  walls,  as 
well  as  the  upper  parts  of  the  blank  spaces  between  the  doors 
and  windows,  may  be  furnished  with  brackets  for  the  busts  of 
distinguished  chemists,  or  hooks  upon  which  to  hang  their  framed 
portraits ;  and  the  lower  part  beneath  the  windows  may  be  reserved 
for  chairs  k.  The  blank  space  j  over  the  door  leading  into  the 
operating  room  can  be  occupied  with  a  cheap  Yankee  clock,  a 
very  requisite  and  convenient  piece  of  furniture  in  a  laboratory. 

It  is  necessary  to  be  minute  in  describing  the  arrangement, 
for,  unless  there  is  some  system,  there  can  be  no  economy  of 
space,  and  hence  much  confusion.  In  the  centre  of  the  wing  is 
the  chimney  a,  and  immediately  opposite,  in  near  juxtaposition, 
the  hot-water  stove  b  which  warms  the  apartment. 

Against  the  off  wall,  and  to  the  left  of  the  stove,  is  the  mineral 
case.  There  should  be  at  least  two  of  these,  and  the  second  may 


26 


THE   OFFICE — THE  WRITING-DESK. 


Fig.  6. 


occupy  the  vacancy  in  the  wall  immediately  opposite.  The 
positions  of  these  cases  are  represented  in  Plate  2  by  the  letters 
c  and  d.  Fig.  6  below  gives  an  idea  of  their  form  and  construc- 
tion. They  are,  in  fact,  nothing  more  than  mere  wardrobes,  with 

the  shelves  and  drawers  substituted  by 
sliding  trays.  They  can  be  of  some 
cheap  wood,  and  painted.  The  slid- 
ing trays  are  much  more  convenient 
than  drawers,  and  present  less  lia- 
bility of  damage  to  their  contents,  as 
they  admit  of  easier  handling,  it 
being  frequently  necessary  to  draw 
them  out  to  examine  their  contents. 
The  specimens  which  they  are  to 
preserve,  secure  from  dust  and  un- 
warrantable handling,  should  be  sepa- 
rately encased  in  shallow  pasteboard 
boxes,  each  bearing  the  name  and 
locality  of  the  mineral.  The  mine- 
rals should  be  so  classified  that  only  one  species  may  be  assigned 
to  a  tray,  which  should  be  labelled  on  its  face  accordingly.  The 
trays  may  be  of  3  to  4  inches  depth,  with  intervening  spaces  of 
an  inch  or  less,  and  the  number  of  them  in  proportion  to  the 
dimensions  of  the  case,  which,  in  height,  should  not  exceed  eight 
feet. 

There  ought  to  be,  properly,  another  case  of  smaller  dimen- 
sions, for  the  reception  of  such  minerals  and  specimens  as  may 
have  been  subjected  to  analysis.  They  should  be  labelled  to 
correspond  with  the  memoranda  of  them  noted  in  the  record 
book  of  the  laboratory,  as  instances  frequently  arise  of  a  neces- 
sity of  future  reference,  and  hence  the  policy  of  this  arrangement. 
The  writing-desk,  which  is  the  main  piece  of  furniture  of  this 
room,  should  stand  against  the  back  wall  of  the  office,  as  shown 
in  Plate  2  by  letter  e.  Its  form  and  construction  are  represented 
by  Fig.  7.  It  is  made  to  occupy  as  little  room  as  possible,  and 
yet  at  the  same  time  to  possess  all  the  requisite  conveniences  of 
an  escritoir.  The  small  drawers  and  cuddies  are  concealed  by  a 
cover  or  writing  flap,  which  is  supported  by  metal  quadrants,  and 
goes  up  perpendicularly,  forming,  when  closed,  a  part  of  the  front. 


TUB   OFFICE — THE   DRAWING-TABLE. 


27 


Fig.  7. 


The  drawers  are  well  adapted  for  stationery,  and  the  cells  for  the 
manuscript  papers,  notes,  letters,  &c.  The  doors  in  the  lower  part 
cover  a  series  of  shelves,  which  may  be  used  as  receptacles  for  accu- 
mulating papers,  which  should  be  filed 
away  in  bundles,  and  indorsed  with 
memoranda  of  their  contents.  The 
sliding  flap,  as  well  as  the  doors 
beneath,  are  fitted  with  locks ;  and 
the  desk,  when  closed,  has  the  ap- 
pearance of  a  handsome  secretary ; — 
and  thus  we  have  the  means  of  pre- 
serving its  privacy  during  our  tem- 
porary absence  from  the  office.  To 
the  right  and  left  of  the  desk,  the 

blank  spaces  of  the  side  and  end  walls  must  be  appropriated  to 
shelving  for  the  library.  It  is  better  to  have  them  elevated, 
rather  than  resting  immediately  upon  the  floor.  The  pedestals 
may  be  two  feet,  and  the  shelving  above,  six  feet  high.  The 
pedestals,  or  base,  should  be  broader  than  the  shelving  above,  and 
may  be  fitted  with  deep  slats  for  the  reception  of  charts,  diagrams, 
pamphlets,  &c.  The  upper  shelves  are  to  be  reserved  exclusively 
for  books ;  and  to  protect  them  from  the  dust,  must  be  enclosed 
with  curtains,  hung  as  before  directed.  The  position  of  this 
shelving  is  shown  in  Plate  2  by  the  letters///. 

The  vacant  spaces  upon  the  wall  above  the  shelving  and  cases 
may  be  very  appropriately  used  for  hanging  maps,  mounted 
charts,  diagrams,  &c.,  selecting  such  as  are  of  frequent  use  for 
reference. 

The  table  gl  standing  midway  between  the  centre  and  front  of 
the  room,  is  one  of  the  greatest  conveniences  of  the  apartment. 
It  combines  in  its  construction  the  requisites  of  a  drawing-table 
and  chest,  a  centre-table,  and  map-stand.  Walnut  is  the  most 
preferable  material  for  this  piece  of  furniture,  which  should  be 
strongly  made,  and  firmly  fastened  to  the  floor  by  iron  clamps 
and  screws.  Its  superficial  dimensions  are  4  by  2  feet,  and  its 
height  38  inches.  The  top,  of  an  inch  thickness,  is  a  rising  flap, 
and  covers  a  shallow  tray,  or  receptacle  for  paper,  drawing  ma- 
terials, and  unfinished  drafts.  The  prop-stick  catches  in  a  gra- 
duated ratchet,  indented  in  the  flap,  and  permits  the  raising  of 


28 


BALANCE-ROOM. 


the  top  to  any  desired  inclination,  and  renders  it  available  as  a 

writing  or  drawing-desk.    By 
8-  lowering   the   top,  so   as   to 

make  a  level  table,  a  flat  sup- 
port is  formed  for  the  examina- 
tion of  folios,  large  drafts,  and 
charts,  which  require  a  broad 
spread  and  careful  usage. 
The  shelving  beneath  is  very 
convenient  for  the  preserva- 
tion of  this  portion  of  the 
library,  for  being  of  adequate 
dimensions,  the  drawings  need 
not,  necessarily,  be  crumpled, 
in  being  placed  away. 
A  small  step-ladder,  for  convenience  in  reaching  the  top 
shelves  of  the  mineral  and  book-cases,  is  very  necessary  in  the 
office,  as  well  also  in  the  other  apartments  of  the  laboratory. 


CHAPTER  II. 


THE   BALANCE-ROOM. 

THE  small  room  D  in  the  rear  of  the  office,  and  from  which  it 
has  been  partitioned,  has  a  width  of  eight  feet,  and  is  to  be  ex- 
clusively used  as  the  balance-room,  and  store  for  metallic  appa- 
ratus. They  are  thus  housed  in  a  close,  dry  apartment,  to 
preserve  them  from  dampness  and  injury,  and  from  deleterious 
exhalations  to  which  they  would  be  exposed  in  the  working-room 
during  the  progress  of  operations.  The  two  balances  occupy 
separate  places,  and  should  rest  upon  solid  shelves,  firmly  fast- 
ened to  brackets  set  into  the  wall.  These  shelves  stand  imme- 
diately against  the  outer  side  wall,  as  shown  at  letters  g  g  in 
Plate  2.  The  remaining  wall  space  is  fitted  with  curtained 
shelves,  or,  preferably,  glass  cases,  for  the  reception  of  the  me- 
tallic and  other  finer  apparatus  which  require  care  in  their  pre- 
servation. The  entrances  h  h  from  the  office  into  the  main  room 


THE   FURNACE.  29 

are  closed  with  tightly  fitting  doors,  which  may  be  fastened  by 
dead-latches,  and  should  always  be  kept  closed  by  means  of  a 
spring.  Their  dimensions  are  2  feet  10  inches  in  width,  and  7 
feet  height. 

This  apartment  is  also  to  be  kept  warm  by  means  of  a  water- 
stove  placed  in  the  corner  or  other  convenient  position. 


CHAPTER  III. 

THE   FURNACE-ROOM. 

PASSING  over  the  operating-room  for  the  present,  we  pro- 
ceed to  describe  the  furnace-room  B,  which  occupies  the  left 
wing  of  the  building  to  the  whole  depth,  without  any  subdivision 
for  other  purposes.  Its  width  is  ten  feet  three  inches.  In 
this  room  are  performed  all  the  operations  requiring  the  use  of 
furnaces,  stills,  and  steam,  and  in  their  progress  generating 
deleterious  fumes,  dust,  or  dirt.  It  is  therefore  necessary  for 
the  comfort  of  the  chemist,  and  the  preservation  of  the  appa- 
ratus, to  keep  the  side  door  z,  (7  feet  high,  and  2-10  wide,)  lead- 
ing into  the  main  apartment,  constantly  closed.  The  front  of  this 
wing  is,  as  to  windows,  identical  with  that  of  the  office.  The 
free  admission  of  light,  which  is  effected  by  means  of  the  two 
long  front  and  three  elevated  side  windows,  is  as  requisite  in  this 
as  in  the  operating-room.  The  chimney  of  this  apartment  occu- 
pies the  centre  of  the  outer  wall,  and  receives  the  main  flue,  fur- 
nishing draft  to  the  main  furnace  and  two  lateral  branches.  Of 
these  two  branch  flues,  both  of  which  have  circular  openings, 
with  movable  tin  stopples,  one  is  for  the  reception  of  the  smoke- 
pipe  of  the  still  furnace  E,  and  the  other  for  that  of  the  steam 
generator  F  ;  or,  when  not  in  use  otherwise,  for  the  portable 
blast,  and  other  furnaces.  These  flues  are  fitted  with  dampers 
to  regulate  the  draught;  and  the  circular  opening,  when  not 
occupied  with  apparatus,  or  as  vent-holes  for  the  dispersion  of 
noxious  vapors,  should  be  kept  covered,  so  as  to  preserve  unim- 
paired the  draught  of  the  main  furnace. 

The  Furnace. — The  furnace  G,  which  is  in  constant  use  for 


30 


THE    FURNACE. 


the  ordinary  operations  of  the  laboratory,  o'ccupies  the  centre  of 
the  outer  wall.  One  of  simple  construction  is  described  by 
Faraday,  to  whom  we  are  indebted  for  drawings,  &c. 

"  Being  in  constant  requisition  as  a  table,  it  should  be  about 
34  or  35  inches  in  height.  The  brickwork  should  measure  36 
by  20  inches,  and  the  iron  plate,  including  sand-baths,  40  by  28 
inches.  A  warm  air  chamber  may  be  built  in  the  walls  beneath 
the  flue.  Projecting  spikes  should  be  fastened  into  one  or  two 
sides  of  this  chamber,  to  hold  a  temporary  shelf  when  required. 

"  Precipitates,  filters,  and  other  moist  substances  put  into  such 
a  chamber,  are  readily  and  safely  dried.  The  hot  air  causes 
evaporation  of  the  water,  whilst  the  current  removes  the  rising 
vapor.  The  chamber  is  very  useful  in  effecting  the  slow  evapora- 
tion of  liquids,  and  also  for  hot  filtrations,  when  the  entering 
current  of  air  is  of  a  temperature  sufficient  for  the  purpose. 

"The  principal  part  of  this  furnace  is  necessarily  of  brick- 
work, only  the  top  plate  with  the  baths  and  the  front,  being  of 
iron.  The  front  is  a  curved  iron  plate,  having  two  apertures 
closed  by  iron  doors,  one  belonging  to  the  fire-place,  and  the 
other  to  the  ash-pit.  It  is  34  inches  high,  and  14  inches  wide. 
The  ash-hole  door  moves  over  the  flooring  beneath ;  the  bottom 
of  the  fire-place  door  is  22  inches  from  the  ground,  and  the  door 
itself  is  8  J  inches  by  7.  This  front  is  guarded  within  at  the  part 
which  encloses  the  fire  by  a  strong  cast-iron  plate,  having  an 
opening  through  it  corresponding  to  the  door  of  the  fire-place. 

It  has   clamps  attached  to  it, 

^  ®; which,    when   the   furnace   is 

built  up,  are  enclosed  in  the 
brickwork." 

In  the  setting  or  building 
of  the  furnace,  two  lateral 
brick  walls  are  raised  on  each 
side  the  front  plate,  and  a  ba-jk 
wall  at  such  a  distance  from  it 
as  to  leave  space  for  the  ash- 
hole  and  fire-place  ;  these  walls 
•  are  lined  with  Welsh  lumps, 

where  they  form  the  fire-chamber ;  two  iron  bars  are  inserted  in 
the  course  of  the  work  to  support  the  loose  grate  bars  in  the 


THE   FURNACE.  31 

usual  manner,  the  grate  being  raised  19  inches  from  the 
ground.  The  side  walls  are  continued  until  of  the  height  of 
the  front,  and  are  carried  backward  from  the  front  in  two 
parallel  lines,  so  as  to  afford  support  for  the  iron  plate  which  is  to 
cover  the  whole.  The  back  wall  of  the  fire-place  is  not  raised 
so  high  as  the  side  walls  by  six  inches  and  a  half,  the  interval 
which  is  left  between  it  and  the  bottom  of  the  sand-bath,  being 
the  commencement  of  the  flue  or  throat  of  the  furnace.  In  this 
way  the  fire-place,  which  is  fourteen  inches  from  back  to  front, 
and  nine  inches  wide,  is  formed,  and  also  the  two  sides  of  the 
portion  of  horizontal  flue  which  belongs  to  the  furnace,  and  is 
intended  to  heat  the  larger  sand-bath.  The  bottom  of  this  part 
of  the  flue  may  be  made  of  brickwork,  resting  upon  bearers  laid 
on  the  two  side  walls,  or  it  may  be  a  plate  of  cast  iron  resting 
upon  a  ledge  of  the  brickwork  on  each  side,  and  on  the  top  of  the 
wall,  which  forms  the  back  of  the  fire-place.  When  such  an  ar- 
rangement is  adopted,  the  plate  must  not  be  built  into  the  brick- 
work, but  suffered  to  lie  on  the  ledges,  which  are  to  be  made  flat 
and  true  for  the  purpose ;  for,  if  attached  to  the  walls,  it  will, 
by  alternate  expansion  and  contraction,  disturb  and  throw  them 
down.  The  ends  of  the  side  walls,  forming  as  it  were  the  back 
of  the  furnace,  may  be  finished  either  by  being  carried  to  the 
wall  against  which  the  furnace  is  built,  or  enclosed  by  a  piece  of 
connecting  brickwork,  to  make  the  whole  square  and  complete ; 
or  a  warm  air  cupboard  may  be  built  in  the  cavity  beneath  the 
flue,  and  the  door  made  to  occupy  the  opening  between  the  walls. 
Occasionally  the  flue  may  be  required  to  descend  there,  and  pass 
some  distance  under  ground.  These  points  should  be  arranged 
and  prepared  before  the  plate  constituting  the  top  of  the  furnace 
is  put  oh  to  the  brickwork,  so  that  when  the  plate  with  its  sand- 
baths  are  in  their  places,  they  may  complete  the  portion  of 
horizontal  flue  by  forming  its  upper  side. 

The  size  of  this  plate  is  the  first  thing  to  be  considered,  and 
having  been  determined  upon,  from  a  consideration  of  the  situa- 
tion to  be  occupied  by  the  furnace,  and  the  places  of  the  sand- 
baths  also  having  been  arranged,  the  brickwork  must  then  be 
carried  up,  so  as  to  correspond  with  these  determinations,  and 
with  the  plate  itself,  which  in  the  meantime  is  to  be  cast.  The 
sand-baths  and  the  plate  are  to  be  formed  in  separate  pieces. 


32  THE   FURNACE. 

The  bath  over  the  fire  is  best  of  a  circular  form,  and  of  such 
diameter  that,  when  lifted  out  of  its  place,  it  may  leave  an  aper- 
ture in  the  plate  equal  in  width  to  the  upper  part  of  the  fire-place 

beneath ;  so  that  a  still,  or 
- 10- cast-iron  pot,  or  a  set  of  rings, 
may  be  put  into  its  place  over 
the  fire.  The  other  sand- 
bath  must  be  of  such  a  form 
as  to  correspond  with  the 
shape  and  size  of  the  flue  be- 
neath. These  vessels  are  to 
be  of  cast  iron,  about  three- 
tenths  of  an  inch  thick ;  their 
depth  is  to  be  two  inches  and  a  half  or  three  inches,  and  they 
are  to  be  cast  with  flanches,  so  as  to  rest  in  the  corresponding 
depressions  of  the  plate,  that  the  level  of  the  junctions  may  be 
uniform.  This  will  be  understood  from  the  accompanying  sec- 
tion of  the  furnace,  given  through  the  line  A  B  of  the  view.  It 
is  essential  that  these  sand-baths  be  of  such  dimensions  as  to  fit 
very  loosely  into  the  apertures  in  the  plate,  when  cold,  a  space 
of  the  eighth  of  an  inch  or  more  being  left  all  round  them,  as 
shown  in  the  section,  otherwise,  when  heated,  they  will  expand 
so  much  as  entirely  to  fill  the  apertures,  and  even  break  the 
plate.  The  plate  itself  should  be  half  an  inch  thick. 

When  the  plate  and  its  sand-baths  are  prepared,  and  the  brick- 
work is  ready,  the  furnace  is  finished  by  laying  the  plate  on  the 
brickwork,  with  a  bed  of  mortar  intervening.  If  the  walls  are 
thin,  or  any  peculiarity  in  their  arrangement  occasions  weakness, 
they  should  be  bound  together,  within  by  cranks  built  into  the 
work,  and  without  by  iron  bands.  The  alternate  changes  of 
temperature  from  high  to  low,  and  low  to  high,  to  which  the  fur- 
nace is  constantly  subject,  renders  it  liable  to  mechanical  injury, 
in  a  degree  much  surpassing  that  which  would  occur  to  a  similar 
piece  of  brickwork,  always  retained  nearly  at  one  temperature." 
The  square  space  enclosed  by  the  fire-place  and  flues  may  be 
converted  into  an  excellent  drying  or  warm  air  chamber  if  de- 
sired. 

Cast  iron  is  the  best  material  for  these  baths,  for,  though  liable 
to  be  cracked  when  first  heated,  by  their  unequal  expansion  in 


THE   FURNACE — THE    SAND-BATHS. 


33 


Fig.  11. 


different  parts,  they  do  not  warp  and  assume  the  irregular  and 
inconvenient  shapes  that  wrought  iron  acquires  under  similar 
circumstances. 

"  These  baths  should  have  washed  sea-sand  put  into  them  ;  it 
is  heavy,  and  occasions  no  dust  when  moved,  whilst,  on  the  con- 
trary, unwashed  and  bad  sand  contains  much  dirt,  and  occasions 
great  injury  in  experimenting.  A  piece  of  straightened  iron 
hoop,  about  twelve  inches  in  length,  should  lie  on  the  furnace,  as 
an  accompaniment  to  the  baths,  being  a  sort  of  coarse  spatula 
with  which  to  move  away  the  sand. 

"  The  circular  sand-bath  is  frequently  replaced  by  a  set  of  con- 
centric iron  rings,  or  a  cast-iron  pot. 
The  rings  are  convenient  for  leaving  an 
aperture  over  the  fire  of  larger  or  smaller 
dimension,  according  as  a  smaller  or 
larger  number  are  used  at  once ;  and 
being  bevelled  at  the  edges,  fit  accu- 
rately into  each  other,  without  any  risk 
of  becoming  fixed  by  expansion.  The 
external  one,  like  the  sand-baths,  should 
be  made  smaller  than  the  depression  in 
the  furnace  plate  in  which  it  rests.  The 
iron  pots  are  of  various  sizes,  and  are 

adapted  to  the  furnace  by  means  of  the  rings;  a  red  heat  is 
easily  obtained  in  them  for  sublimation." 

In  many  instances,  where  economy  is  of  prime  importance, 
the  foregoing  sand-bath  may  be  replaced  by  an  ordinary  cylinder 
stove,  the  pipe  of  which  leading  into  a  four-sided  sheet  iron  box, 
divided  into  flues  by  partitions,  imparts  its  heat  in  transitu  to 
the  chimney.  The  top  of  this  box,  when  covered  with  sand, 
forms  the  sand-bath.  That  portion  of  its  surface  immediately 
over  the  first  flue,  is  the  hottest.  The  remote  or  cooler  end,  is 
best  adapted  for  gradual  digestions,  evaporations,  &c. ;  and  so  by 
these  flues  there  is  a  means  of  graduating  the  temperature  of  the 
bath.  The  top  of  the  stove  itself  being  directly  over  the  fire, 
makes  an  excellent  bath  for  those  operations  requiring  a  higher 
temperature ;  and  by  a  djusting  an  outer  casing  of  tin  plate  to  the 
circumference  of  the  stove,  a  drying  chamber  may  be  formed. 

The  steam  generator  (Fig.  13)  when  used  as  a  stove  for  heat- 

3 


34 


THE    FURNACE- — THE    HOOD. 


ing  the  apartment,  answers  equally  well  to  heat  the  bath,  it  being 
only  necessary  to  conduct  its  smoke-pipe  into  the  iron  box  instead 
of  leading  it  directly  into  the  chimney. 

To  prevent  contamination  of  the  atmosphere  of  the  apartment, 
by  admixture  with  the  deleterious  fumes  evolved  during  the 
various  operations  of  digestion,  fusing,  melting,  heating,  and 
evaporating  in  progress  upon  the  sand-bath  and  in  the  furnaces, 
there  should  be  firmly  fastened  to  the  ceiling  and  immediately 
over  its  surface,  extending  beyond  its  superficies  some  four  inches 
all  around,  a  sheet-iron  hood,  of  form  at  the  base  corresponding 
with  that  of  the  top  of  the  furnace.  The  barrel  of  this  hood  may 
pass  either  directly  through  the  ceiling  and  roof  into  the  atmo- 
sphere, or  else  be  formed  into  an  elbow,  leading  into  the  main  flue 
of  the  chimney.  In  either  case,  the  draft  must  be  thorough,  so 

as  to  aiford  a  free  egress  of 
the  fumes  into  the  atmosphere 
without.  It  should  also  be 
immovably  fixed  by  rod  iron 
stretchers,  and  well  payed 
over  with  zinc  paint.  The 
fixture  is  represented  by  Fig. 
12.  It  should  descend  as  near 
to  the  surface  of  the  bath  as 
convenience  of  manipulation 
will  allow ;  and  to  prevent 
any  accumulation  of  dirt  in 
the  interior,  it  should  be  fre- 
quently brushed  out  with  a 
soft  brush ;  and  for  protection  to  the  vessels  on  the  sand-bath, 
against  falling  particles,  the  top  of  the  furnace  should,  during 
the  operation,  be  covered  with  paper.  It  is  advisable  at  all 
times,  independently  of  the  foregoing  suggestion,  to  keep  each 
vessel  covered  with  plates  or  clean  white  paper,  which,  while 
protecting  against  dirt,  offers  no  impediment  to  the  processes  of 
evaporation,  digestion,  &c.  If  the  hood,  instead  of  being  fixed, 
is  counterpoised,  so  as  to  admit  of  ready  depression  or  elevation 
at  will,  it  is  a  little  more  convenient ;  but  that  arrangement  has 
the  disadvantage  of  liability  to  accident,  for  a  carelessness  in 
fastening  the  suspension  cords  may  create  a  very  annoying  da- 


THE    STEAM   GENERATOR. 


35 


Fig.  13. 


mage.  Of  course,  this  mode  of  hanging  the  hood  can  only  be 
adopted  where  the  barrel  or  pipe  is  straight,  and  leads  directly- 
through  the  roof;  and  then  to  protect  the  exit  hole  from  the 
wear  and  tear  consequent  upon  the  abrasion  of  its  circumference, 
it  should  be  fitted  with  an  earthenware  cylinder ;  and  further- 
more, to  prevent  the  entrance  of  rain  through  the  slight  open- 
ings, there  should  be  a  spreading  flange  around  the  protruding 
portion  of  the  barrel  of  the  hood,  near  the  roof. 

Furnace. — The  air  or  wind  furnace  of  a  laboratory  is  gene- 
rally a  fixture  made  of  refractory  brickwork  and  iron ;  but  the 
Universal  Furnace  and  Barren's  Blast  Furnace,  described  in  Chap- 
ter XI,  are  more  convenient  portable  apparatus,  which  will  serve 
for  all  the  purposes  of  the  laboratory. 

The  Steam  Generator. — To  the  right  of  the  furnace,  at  a 
convenient  distance,  is  the  portable  steam  generator  F,  with  its 
smoke  pipe  leading  into  the  circular  opening  of  the  lateral  flue 
opposite.  It  has  a  stove-like  form,  is  compact,  requires  no  brick- 
work, and  but  very  little  fuel,  and  can  be  set  up  and  removed  at 
will,  when  it  is  desired  to  occupy  the 
flue  with  other  .apparatus.  The  only 
fixtures  requisite,  in  addition  to  the 
machine,  are  feed  pipes  to  convey  the 
water,  and  conduits  for  the  passage  of 
the  steam.  It  is  a  most  convenient  ap- 
paratus for  the  laboratory,  being  alike 
handy  for  economically  supplying  hot 
water  to  all  parts  of  the  building,  and 
for  boiling  substances,  where  the  direct 
admission  of  steam  is  preferable;  and 
also  for  heating  the  steam  series  in  the 
range  a  little  to  its  left.  This  mode  of 
applying  heat,  having  the  great  advan- 
tages of  safety,  convenience,  and  regu- 
larity, is  absolutely  requisite  in  many 
cases  where  the  naked  fire  does  not  offer 
that  uniformity  of  temperature  which  the 
alterability  of  certain  substances  under 
process  renders  necessary.  Fig.  13  repre- 
sents the  apparatus.  By  means  of  coup- 
ling screws  and  flexible  lead  pipe,  the  steam  may  be  carried  to 


36     *  LABORATORY   JACK. 

any  reasonable  distance  in  any  direction,  thus  affording  great 
facility  in  many  operations ;  as  the  loss  by  condensation  in  thus 
conveying  it  is  inconsiderable.  In  very  cold  apartments,  how- 
ever, when  the  conduit  pipe  is  of  any  great  length,  it  may 
very  properly  be  enveloped  with  woollen  listing  or  other  bad  con- 
ducting materials.  The  lower  cock  in  the  figure  connects  with 
the  feed  pipe.  The  three  smaller  cocks  above,  and  placed  equi- 
distant from  each  other,  are  try  cocks,  to  ascertain  the  height  of 
the  water,  by  which  its  supply  must  be  accordingly  regulated. 
The  steam  conduits  are  coupled  by  a  cock  fitted  to  the  top  of  the 
generator. 

The  door  in  the  lower  part  is  for  the  introduction  of  the  coal 
into  the  fire  hole. 

For  laboratories  of  public  institutions,  or  for  any  laboratory 
which  it  is  desirable  should  be  complete  in  its  arrangement,  the 
better  plan  will  be  to  combine  the  generator,  sancKbath,  and  dry- 
ing chamber  in  one  and  the  same  piece  of  apparatus.  This  is 
done  to  a  certain  extent  in  Beindaff's  apparatus,  which  will  here- 
after be  described ;  but  that  implement  is  only  adapted  to  small 
operations.  We  have,  therefore,  aided  by  the  practical  skill  of 
Matthew  Y.  Forney,  engineer,  of  Baltimore,  devised  an  econo- 
mical and  compact  substitute,  which  is  efficient  for  all  the  pur- 
poses of  a  large  laboratory,  and  may,  from  its  capacity  for  so 
many  uses,  very  properly  be  called  the 

Laboratory  Jack. — It  consists  wholly  of  metal,  and  may  be 
set  up  like  a  stove  in  any  position  convenient  to  a  chimney  flue. 
This  is  a  saving  of  all  the  expensive  mason-work  of  other  forms 
of  furnaces  now  in  general  use  for  similar  objects,  and  the 
arrangement,  though  simple,  comprises  all  the  requisites  of  such 
a  structure  in  the  minimum  of  space  and  over  a  single  fire. 

The  apparatus  consists  of  two  parts,  the  frame  and  the  boiler. 
The  first,  with  the  exception  of  the  glass  window,  is  cast  in  iron, 
from  patterns ;  and  the  latter  is  made  of  strong  wrought  iron 
plates.  It  is  very  essential  that  all  the  workmanship  shall  be 
exact,  for  unless  the  various  parts  are  closely  adjusted  at  the 
joints,  the  machine  will  be  wanting  in  that  neatness  of  appear- 
ance which  otherwise  would  render  it  an  ornament  to  the  apart- 
ment. 

The  annexed  drawings  show  the  apparatus  upon  a  scale  of  one 


LABORATORY  JACK. 


37 


twenty-fourth  its  actual  size,  Fig.  14  being  a  front  view,  Fig. 
15  a  side  view,  and  Figs.  16  and  17  longitudinal  and  transverse 
sections. 

Fig.  14. 


For  convenience  of  illustration,  we  will  divide  the  frame  or 
stand  into  an  upper  and  lower  story.  The  front  and  sides  of  the 
upper  story  are  formed  of  sash-work,  the  rear  and  top  of  stiff 
sheet  iron  plate ;  and  this  enclosure  covers  the  sand-bath  form- 
ing the  top  of  the  lower  story.  The  front  window  is  stationary, 
but  each  of  those  at  the  sides  are  hung  with  counterpoises  con- 
cealed in  the  corner  pillars ;  this  facility  for  raising  and  lowering 
them  being  indispensable  to  prevent  damage  to  vessels  in  placing 
them  or  removing  them  from  the  bath.  The  bath  is  also  ledged 
around  its  circumference,  with  soap-stone  slabs  of  about  one 
inch  thickness  and  six  inches  width,  so  as  to  provide  against  the 
breakage  of  glass  or  other  fragile  vessels,  in  case  they  should  be, 
temporarily,  placed  there  on  being  taken  from  the  bath.  The 
durability  of  that  material,  its  resistance  of  the  action  of  corro- 


88 


LABORATORY   JACK. 


Fig.  15. 


sive  agents,  and  limited  power  of  conducting  heat,  render  it  mucli 
more  suitable  for  this  purpose  than  metal.  The  four  slabs  form- 
ing the  ledge  are  so  fitted  as  to  present  a  level  and  smooth  sur- 
face, in  order  that  the  base  of  the  sash  may  fit  closely  to  it. 

As  the  emanations  from  the  vessels  on  the  sand-bath  are  always 
more  or  less  deleterious,  provision  is  made  for  their  uninterrupted 
passage  into  the  chimney  through  a  register  like  the  one  already 
described  at  page  19,  and  which  is  set  at  the  top  of  the  rear  of  the 
jack,  and,  by  means  of  a  pipe-connection,  is  made  to  penetrate 
into  the  flue  against  which  the  jack  is  placed.  In  this  way,  any 
accumulation  of  fumes  within  the  glass  enclosure  is  prevented ; 
so  that,  when  the  windows  are  raised,  as  may  be  necessary,  there 
will  be  little  or  none  to  escape  and  contaminate  the  atmosphere 

of  the  laboratory. 

The  lower  story  consists  of 
the  sand-bath,  a  cylindrical 
boiler  of  about  25  gallons'  capa- 
city, with  its  fire-place  and  ash- 
hole  in  the  centre  beneath,  and 
spacious  drying-chambers  at  the 
sides. 

The  sand-bath  i  i  is  a  cast 
iron  box  forming  the  cap  of  the 
fire-place  b  5,  which  receives 
its  fuel  through  the  doorway 
d.  The  heating-chamber  is  so 
planned,  that  the  draught  enter- 
ing at  e,  Fig.  14,  follows  the 
direction  of  arrows  1  1  until  it 
reaches  the  extreme  end  of  the 
boiler,  where  it  divides  to  rise  in 
two  lateral  currents,  as  shown 
by  arrows  2,  2,  2',  2',  Fig.  16, 
and  then  pass  forward  through 
the  openings  //  to  the  front  of 
the  boiler,  where  they  turn  into 
the  flue  g  g.  Fom  this  latter  it  continues  back  in  the  direction 
of  the  arrows. 3  3,  Fig.  17,  to  the  flue  h  leading  into  the  chim- 
ney. This  winding  course  graduates  the  heat  of  the  bath  to 


LABORATORY    JACK. 


39 


different  degrees, — the  hottest  temperature  being  in  that  part 
where  the  draught  first  strikes  the  bottom  plate,  and  the  most 
moderate  over  the  exit  flue.  The  heat  of  the  other  portions 
varies  according  to  proximity  or  remoteness  in  regard  to  these 
two  extreme  positions.  This  multiplicity  of  temperatures  by 
means  of  one  fire,  and  always  ready  for  use,  will  be  found  a  great 
convenience.  A  damper  for  regulating  the  fire  is  placed  at  5  5, 
Fig.  17,  where  the  two  flues //enter  the  flue  g  g. 

The  boiler  a  a,  which,  as  before  directed,  should  be  made 
neatly  and  strong,  is  placed  below  the  bottom  and  centre  of  the 
sand-bath,  and  extends  the  whole  depth  of  the  jack.  On  the 
front  end  is  the  safety-valve  p  p,  with  a  side  nozzle  q  for  con- 
necting the  distillation  and  steam-pipe,  as  will  be  described 
directly.  Immediately  below  it  are  the  guage-cocks  r  r  r,  for 
determining  the  height  of  water  in  the  boiler  ;  arid  under  these, 

Fig.  16. 


again,  is  the  hand-hole  s  for  cleaning  the  boiler,  as  may  become 
necessary  by  the  accumulation  of  deposited  matters. 

The  boiler,  from  its  position,  will  be  always  more  or  less  heated 
by  the  fire  beneath,  which  is  kept  constant,  for  the  purpose  of 
maintaining  the  heat  of  the  sand-bath  during  the  night  as  well 
as  the  day,  so  that  there  may  be  no  interruption  to  the  digestions 
and  other  processes  in  action  upon  the  bath  during  the  absence 
of  the  attendant.  This  circumstance  is  also  made  subservient, 
in  the  construction  of  the  jack,  to  a  very  necessary  provision,  and 
that  is  a  continuous  supply  of  distilled  and  warm  waters,  and  a 


40 


LABORATORY   JACK. 


regular  uninterrupted  temperature  in  the  adjacent  drying-cham- 
bers at  the  sides.  When  the  use  of  the  boiler  is  to  be  restricted 
to  these  objects,  the  heat  must  be  kept  down ;  for  which  purpose, 
there  is  a  sliding  shelf  I  I  in  the  fire-place.  This,  on  being 
drawn  forward,  as  shown  in  Fig.  17,  turns  the  draught  in  the 
direction  of  the  arrows  1  1,  and  thus  intercepts  the  immediate 
action  of  the  fire  upon  the  boiler.  The  shelf  is  of  cast  iron  :  and 
has  a  grooved  rim  for  holding  in  place  a  soap-stone  lining, 
which  is  necessary  to  diminish  the  conducting  power  of  the 
metal.  As  a  further  means  of  restricting  the  heat  within  the 
proper  degree,  there  are  openings  1 1  for  admitting  cold  air  under 
the  boiler  ;  but  as  it  will  be  necessary  to  use  steam  occasionally, 
they  are  fitted  with  covers  for  shutting  off  the  current  in  such  cases. 
The  heat  obtained  as  above  is  sufficient  to  evaporate  the  water 
in  the  boiler  and  send  it  off  in  the  form  of  vapor,  to  be  con- 
densed as  distilled  water ;  but,  to  convert  it  into  steam,  the 
whole  force  of  the  fire  is  requisite.  This  is  applied  by  pushing 
the  sliding-shelf  backwards,  so  as  to  close  the  opening  m,  Fig. 
17,  and  at  the  same  time  expose  the  lower  portion  of  the  boiler 
to  the  direct  action  of  the  fire ; — the  draught  then  passing  up- 
wards in  the  direction  of  the  arrows  I  0,  through  the  openings 
m  n,  Fig.  17.  The  fire-place  and  bottom  of  the  ash-pit  are 
lined  with  soap-stone,  to  prevent  the  burning  of  the  sides  and 
danger  from  fire  to  the  floor  upon  which  the  jack  rests. 

The      drying-chambers 

Flg' 17' ^^^  j  j  j  j  are  spacious  apart- 
ments, which  derive  a  con- 
tinuous warmth  from  the 
sides  of  the  adjacent  boiler 
and  fire-place ;  and  the 
temperature  is  of  a  degree 
most  suitable  for  the  drying 
operations  of  the  labora- 
tory. They  are  always  ready 
for  use ;  and  to  add  to 
their  convenience,  the  ends 
are  cast  with  projections 
at  proper  intervals,  for  the 
support  of  iron  shelves.  All  of  these  shelves  are  movable,  and 


LABORATORY    JACK.  41 

I  '  '  '•     ''         7  *^ 

some  are  bored  with  holes  throughout  their  surface,  so  as  to  make 
the  chamber  available  for  large  vessels  and  funnels,  as  well  as  for 
those  of  smaller  dimensions.  The  doors  k  Jc  afford  access  to  the 
interior  as  may  be  necessary. 

To  carry  out  the  design  of  making  this  apparatus  self-managing 
as  far  as  possible,  the  boiler  is  fed  from  a  suitably  adapted 
reservoir,  Fig.  16,  in  proportion  as  it  loses  water  by  evaporation. 
The  supplies  are  admitted  through  the  opening  v,  and  the  pipe 
#,  connecting  with  a  wooden  cistern  v  v,  placed  in  any  con- 
venient corner  of  the  apartment.  This  pipe  may  be,  for  the 
sake  of  protection  and  convenience,  laid  under  the  floor,  but,  in 
such  case,  it  will  be  necessary  to  wrap  it  with  several  layers  of 
woollen  listing,  or  else  to  imbed  it  deeply  in  straw,  to  prevent 
freezing  in  cold  weather.  The  level  of  the  water  in  the  reservoir 
is  kept  constantly  in  adjustment  with  that  in  the  boiler,  by  means 
of  the  valve-cock  w  ;  and  to  regulate  this  cock,  there  is  a  hollow 
ball  or  float  g  of  sheet-copper.  As  the  level  of  the  water  in  the 
reservoir  falls,  the  float  of  course  descends  with  it,  and,  in  so 
doing,  opens  the  cock  for  admission  of  water  from  the  hydrant, 
to  replace  that  which  passes  into  the  boiler.  In  like  manner, 
when  the  original  level  is  restored,  the  float  having  risen  with  it, 
closes  the  cock.  This  arrangement  keeps  up  a  supply  of  water 
in  the  boiler  as  fast  as  it  is  diminished  by  evaporation ;  and  this 
affords,  at  all  hours  of  the  day  and  night,  an  abundance  of  dis- 
tilled and  hot  waters  at  little  cost,  as  but  one  fire  is  used ;  and  it 
is  thus  made  to  heat,  at  the  same  time,  the  bath  and  drying- 
chambers. 

For  technical  operations  and  experiments  on  an  extended  scale 
and  requiring  the  use  of  steam,  the  above  apparatus  will  not 
answer  without  a  supplementary  arrangement ;  for  the  pressure 
of  the  steam  generated  in  the  boiler  being  greater  than  that  of 
the  external  atmosphere,  the  water  in  the  reservoir  will  not  act 
alone ;  and  we  have,  therefore,  provided  for  a  forcing  pump. 
This  pump  is  not  shown  in  the  drawings ;  but  it  is  of  ordinary 
construction,  and  worked  by  the  hand.  It  connects  with  the 
pipe  x,  carrying  the  water  from  the  reservoir  to  the  boiler.  The 
reservoir  derives  its  supply  of  water  from  the  hydrant  through 
the  service  pipe  2,  and  it  should  be  fitted  with  a  loose  cover, 
which,  while  keeping  out  the  dust,  will  allow  an  occasional  in- 


42  LABORATORY   JACK. 

spection  of  the  cock,  as  will  be  necessary  to  feel  assured  that  it 
continues  in  good  order. 

The  outlet  for  the  distilled  water  and  ste*am  is  through  a  tinned 
gas  pipe  of  an  inch  diameter,  which  is  attached  by  a  coupling- 
nut  to  the  nozzle  #,  projecting  from  the  side  of  the  valve  p. 
This  tube  rises  upwards  to  the  top  of  the  jack,  when  it  is  bent 
outwards  and  continued  in  a  straight  line  to  the  opposite  wall, 
where  it  is  to  diverge  at  angles  by  means  of  a  T  joint.  To  each 
end  of  these  angular  joints  is  fitted  a  stop-cock  and  connect- 
ing-pipe, turned  interiorly,  as  above  directed.  One  leads  to  the 
steam  series,  and  forms  the  conduit  for  serving  it  and  the  still 
with  steam ;  the  other  conveys  away  the  vaporized  water  to  the 
cooling-worm,  where  it  is  condensed  into  distilled  water.  These 
two  cocks  allow  the  use  of  either  branch,  as  may  be  necessary; 
for  when  the  boiler  is  generating  steam,  the  cock  on  the  branch 
leading  to  the  condenser  is  to  be  closed,  and  vice  versa,  as  it  can- 
not be  used  simultaneously  for  both  purposes. 

The  branches  conveying  the  steam  should  be  thickly  enveloped 
with  woollen  list  to  prevent  loss  of  heat  by  radiation. 

The  condensing  apparatus  consists  of  a  block-tin  worm  and 
tub,  very  similar  to  that  described  when  speaking  hereafter  upon 
the  STILL.  It  is  placed  in  a  remote  corner  of  the  room  and  upon 
a  high  pedestal,  so  that  there  may  be  space  beneath  for  a  vessel  to 
receive  the  distilled  water  as  it  trickles  from  the  worm.  This  re- 
ceiving-vessel is  of  blue  or  white  stoneware,  free  from  lead  glazing, 
and  made  pear-shaped,  with  a  flat  bottom,  and  its  narrow  mouth 
kept  always  protected,  by  a  suitable  cover,  against  entrance  of  dust 
or  absorption  of  acid  fumes.  A  glass  cock  at  the  bottom  is  neces- 
sary for  drawing  off  the  water  when  it  is  needed  for  use.  The  tub 
is  of  zinc  or  galvanized  iron,  and  bevelled  at  the  rim,  so  as  to  present 
a  bed  or  rest  for  a  round-bottom  pan,  when  it  is  desired  to  use  it 
as  an  economical  water-bath  for  large  operations.  The  heat,  in 
such  instances,  is  derived  from  the  water  contained  in  the  tub  and 
surrounding  the  worm,  its  temperature  being  always  high  from 
the  heat  radiated  by  the  aqueous  vapors  passing  through  the 
wown,  in  the  act  of  condensing  into  distilled  water.  The  water 
being  the  condensing  medium,  must,  therefore,  be  replaced  by 
cold  water  as  fast  as  it  becomes  heated,  otherwise  the  condensa- 
tion of  the  vapors  will  be  imperfect.  To  this  end,  there  is  a 

i  •        '       '':;-:;:  \ 


LABORATORY   JACK.  43 

small  annular  opening  near  the  top  of  the  tub,  which  connects 
with  an  external  tube  running  down  the  side  and  out  into  the 
gutter.  Complementary  to  this  opening  is  another  similar  one 
on  the  opposite  side  and  connecting  with  the  hydrant,  but  with 
its  tube  passing  into  the  interior  of  the  tub,  and  down  to  the 
bottom.  When  the  hydrant-cock  is  opened  for  the  admission  of 
cold  water  into  the  tub  or  cooler,  the  hot  water  being  specifically 
lightest,  rises  as  the  cold  water  enters  below,  and  flows  out  at  the 
top  through  the  exit  tube.  The  bottom  of  this  tub  is  fitted  with 
a  cock  for  drawing  off  hot  water,  as  may  be  needed  for  washing 
or  other  purposes. 

By  means  of  this  apparatus,  one  fire  is  made  to  heat  the  sand- 
bath  and  drying-chambers,  furnish  a  constant  supply  of  distilled 
and  hot  water,  and  generate  steam  for  the  various  operations  of 
heating,  boiling,  distilling,  evaporating,  &c.  Besides  these  ap- 
plications, it  is  capable  of  being  adapted  to  many  other  minor 
purposes,  which  experience  must  determine,  as  it  would  require 
too  much  space  to  enumerate  all  its  claims  to  be  appreciated  as  a 
most  serviceable  assistant  in  the  work  of  the  laboratory. 

Steam  Series. — This  is  a  range  of  implements  designed  for  the 
nicer  technical  operations  of  the  laboratory,  or  for  extensive 
experiments  requiring  care  and  an  easily  manageable  temperature 
below  the  boiling-point  of  water.  It  consists  of  five  pieces,  each 
of  which  has  its  appropriate  service ;  and  the  whole  mounted  in  a 
wooden  framework  rests  against  the  back  wall  of  the  apartment, 
as  at  / 1,  Plate  2.  Steam  is  the  heating  medium,  and  the  neces- 
sary supply  may  be  derived  from  the  generator,  Fig.  13,  or  any 
other  form  of  steam  boiler ;  but  we  have  designed  it,  more  espe- 
cially, as  an  appendix  to  our  jack. 

The  great  and  manifold  advantages  of  heating  by  steam  render 
the  boiler  the  chief  source  of  heat  for  the  general  purposes  of  the 
laboratory.  In  all  operations  which  do  not  come  within  its  de- 
gree of  temperature,  the  use  of  the  naked  fire  must  be  resorted 
to,  but  these  cases  are  comparatively  rare,  and  limited  mostly  to 
fusions,  ignitions,  and  certain  operations  which  will  be  more  fully 
explained  in  their  proper  place. 

Fig.  18  presents  an  intelligible  view  of  the  series,  each  imple- 
ment being  shown  in  its  proper  form  and  position.  The  first,  A,  is 
the  still,  of  ten  gallons  capacity,  and  made  of  tinned  copper,  or 


44 


LABOEATOKY   JACK, 

Fig.  18. 


LABORATORY   JACK.  45 

much  better  of  block  tin,  about  three-sixteenths  of  an  inch  thick. 
It  is  composed  of  two  separate  pieces ;  the  body  or  lower  part  a, 
and  the  head  or  capital  6,  the  latter  being  so  nicely  adjusted  to 
the  neck  c,  of  the  former,  as  to  make  a  close  joint  when  the  two 
are  put  together,  as  shown  in  the  drawing.  Its  lower  part  is  en- 
veloped by  a  jacket  0,  forming  a  steam  chamber  of  two  or  three 
inches  space  between  the  inner  and  outer  vessel.  The  rim  of  this 
jacket  is  a  broad  flange,  serving  to  support  the  still  by  a  corre- 
sponding flange  around  the  circumference  of  its  shoulder,  and  to 
make  the  connection  steam  tight,  the  flanges  should  be  interposed 
with  a  piece  of  felt,  and  tightly  bolted  by  nut-screws  or  clamps, 
as  shown  at  p.  The  steam  is  introduced  into  the  chamber,  at  the 
rear  and  just  below  the  flange  aforesaid,  through  a  wrought  pipe 
2,  of  three  and  a  quarter  inches  diameter,  branching  from  the 
main  conduit  M ;  the  stop-cock  ?/,  in  the  middle,  serving  to  shut 
off  the  current  as  may  be  required.  Immediately  in  the  bottom 
centre  of  the  jacket  there  is  a  pipe  d,  leading  downwards  into  a 
gutter,  and  fitted  with  a  valve-cock,  as  a  vent  for  the  escape  of 
condensed  water  and  excessive  steam. 

To  render  the  still  available  for  distillations  at  temperatures 
below  steam  heat,  there  is  a  small  circular  opening  n,  through 
the  united  flanges,  which  leads  into  the  steam  chamber,  and  is 
fitted  with  a  screw-cap  for  closing  it  when  not  in  use.  This 
opening  or  mouth  is  for  the  introduction  of  a  funnel,  which  con- 
veys water  to  the  interior  to  form  a  bath,  as  may  be  necessary. 
Steam  being  then  cautiously  let  on,  the  water-bath  may  be  raised 
to  any  required  temperature  below  212°  F.  The  worm  and  cool- 
ing-tub for  this  still  are  of  the  same  form  and  material  as 
described  for  Fig.  20,  but  their  size  is  necessarily  smaller,  to 
correspond  with  that  of  the  still. 

It  is  scarcely  necessary  to  remark,  that  as  the  mouth  of  the 
still  body  is  wide  and  smooth,  it  may  be  used,  without  the  head, 
as  an  open  vessel,  for  infusions,  evaporations,  &c. 

Next  to  the  still  is  the  steam-kettle,  B,  a  double-bottom  vessel, 
the  interior  of  which  is  tinned  copper  or  block  tin,  supported  in  a 
jacket  exactly  as  described  for  the  still,  A.  It  is  of  five  gallons 
capacity,  and  round  at  the  bottom.  The  branch-pipe,  exit-tube, 
valve-cock,  and  funnel-hole,  have  the  same  relative  positions  in 


46  LABORATORY   JACK. 

this  piece  of  apparatus  as  in  the  preceding.  A  cover  is  provided 
for  boilings  which  require  its  use. 

This  kettle  is  particularly  adapted  for  concentrating  liquids  by 
evaporation,  making  solutions  of  salts  in  hot  water,  and  similar 
operations. 

The  centre-piece  of  the  series  is  an  iron-bound  cedar  tub  C, 
of  form  shown  in  the  drawing.  It  is  of  fifteen  gallons  capacity, 
and  has  a  hinged  cover  for  keeping  out  dust  and  retaining  heat  and 
steam  vapors,  through  the  back  of  which  the  branch-pipe  descends 
into  the  interior  of  the  tub,  and  ends  at  the  bottom  in  a  ring,  per- 
forated upon  its  upper  surface  with  small  holes  for  the  better 
diffusion  of  the  steam.  When  it  is  not  desired  to  use  wet  steam, 
a  close  ring  may  be  substituted  for  the  calendered  circle  of  pipe ; 
and  to  this  end,  the  upper  and  lower  part  of  the  branch-pipe  are 
made  separate,  and  screw  cut  at  the  ends,  to  be  connected  when 
necessary  by  a  coupling-nut  immediately  below  the  cover  of  the 
tub.  This  arrangement  is  necessary  for  the  convenient  substi- 
tution of  the  open  for  the  close  ring,  and  vice  versa.  It  must  be 
added,  however,  that  in  the  use  of  the  close  ring  for  a  dry  heat, 
proyision  is  made  for  the  escape  of  condensed  steam  into  the 
gutter  beneath  by  passing  out  the  exit  end  through  the  side  of 
the  tub.  , 

This  tub  is  very  convenient  for  making  aqueous  solutions  of 
the  soluble  matters  of  plants,  dye-woods,  &c.,  whose  active  prin- 
ciples are  liable  to  become  altered  by  direct  fire  heat.  It  is, 
moreover,  applicable  to  boiling  purposes  generally.  A  cock  near 
the  bottom  allows  the  saturated  liquid  to  be  drawn  off  below,  after 
which,  fresh  water  being  added,  the  boiling  may  be  renewed. 
These  alternate  boilings  and  drainings  may  be  continued  indefi- 
nitely without  the  necessity  of  once  removing  the  solid  contents 
of  the  tub.  To  the  right  of  the  tub  is  the  steam-bath  D,  which 
is  simply  a  round-bottom  bowl  of  iron,  fitted  with  an  exit-tube 
and  valve-cock  in  the  centre  of  the  bottom,  and  after  the  manner 
directed  for  the  other  pieces  of  the  series.  The  flange  serves  as 
a  support  for  the  containing  vessels,  which  are  set  upon  the  top. 
To  contract  the  top  and  adapt  it  to  any  size  of  vessel,  there  is  a 
series  of  concentric  rings,  Fig.  19',  made  of  iron  plates,  and  fitting 
closely  to  the  flange.  The  branch-pipe,  instead  of  entering  at 
the  top  of  the  jacket,  is  led  in  near  the  bottom,  and  made,  by 


LABORATORY  JACK.  47 

*r^      i    ' 

means  of  a  coupling-nut,  to  expand  in  a  circle  perforated  with 
small  holes  throughout  its  upper  surface.  The  steam  ascending 
through  these  openings  in  forcible  jets,  strikes  against  the  bottom 
of  the  vessel  resting  on  the  flange,  and  there  condensing  is  rever- 
berated as  water,  which  finds  escape  through  the  valve-cock.  This 

Fig.  19. 


steam-bath  is  alike  applicable  to  porcelain,  glass,  and  metallic 
vessels,  and  will  be  found  very  convenient  for  evaporations'  in 
capsules  and  distillations  in  glass  retorts;  it  being  only  necessary, 
in  manipulating  with  the  latter,  to  fit  the  ring  with  a  wire  basket 
for  its  support.  The  flow  of  steam  must  be  gentle,  else  the  ves- 
sel will  be  forced  upwards  by  the  confined  steam,  and  possibly  to 
its  damage  and  that  of  its  contents. 

The  last  of  the  series  is  the  stone  still  E.  It  is  made  of  blue, 
salt-glazed  stoneware  after  the  form  shown  by  the  drawing,  s 
being  the  body  and  t  the  head.  Like  the  tin  still,  it  rests,  by  a 
projecting  flange  around  its  shoulder,  upon  the  rim  or  flange  p 
and  an  iron  outer  jacket  0,  which  is  fitted  with  a  valve- cock  and 
funnel-tube  in  the  same  manner  as  the  other  jackets.  The  stone- 
ware flange  being  fragile,  when  brought  in  close  contact  with  the 
iron  flange,  it  is  necessary  to  interpose  a  piece  of  lead  or  thick 
felt  cloth,  and  to  use  clamps  instead  of  nut-screws  for  tightening 
the  connection.  The  head  of  the  still  is  movable,  but  fits  closely 
to  the  neck  m  of  the  body,  so  that  a  steam-tight  joint  may  be 
readily  made  with  the  aid  of  lute.  To  afford  facility  for  intro- 
ducing fresh  charges  without  stopping  the  process  or  disturbing 
the  tub,  there  is  a  stoppered  hole  v  in  the  head  of  the  still. 
The  form  of  the  head  prevents  any  falling  back,  into  the  still,  of 
any  distillate  which  may  condense  in  the  former,  and  sends  it  all 
forward  through  the  beak  into  an  adjacent  worm  of  the  same  ma- 


48 


LABORATORY  JACK. 


terial  as  the  still,  and  arranged  in  a  cooling-tub  after  the  manner 
hereafter  described  for  Fig.  20.  The  branch-pipe  which  conveys 
the  steam  to  the  jacket  of  this  still  enters,  as  usual,  in  the  rear 
and  just  below  the  flange ;  and  it  is  proper  to  add,  that  the  cur- 
rent must  be  gentle  and  cautiously  regulated,  as  the  stoneware 
is  not  capable  of  resisting  as  much  pressure  as  metal.  This  still 
is  used  for  the  distillation  of  acid  mixtures  which  might  act  upon 
metal ;  and  of  ethers  and  similar  substances,  which  are  manage- 
able with  difficulty  in  glass  retorts  over  the  naked  fire  or  sand- 
baths.  Moreover,  being  measurably  free  from  any  liability  of 
breakage,  it  is  adapted  to  the  treatment  of  larger  quantities  than 
could  be  well  operated  upon  in  a  glass  retort. 

It  will  be  seen,  by  reference  to  the  drawing,  that  the  branch- 
pipes  proceed,  severally,  from  a  single  pipe  M  ;  and  this  latter  is 
of  welded  wrought  iron,  and  about  one  and  a  half  inch  diameter. 
It  runs  along  the  wall  immediately  above  the  series,  and  derives 
its  supply  of  steam  from  the  jack  or  generator,  with  which  it 
connects  by  means  of  a  coupling-nut.  A  cock,  G,  serves  to  regu- 
late the  current ;  and  as  the  branch-pipes  are  severally  supplied 
with  a  cock,  it  renders  each  vessel  independent  of  the  rest,  so 
that  they  may  be  put  in  operation  either  singly  or  collectively. 
It  is  proper  to  add,  that  on  first  letting  the  steam  into  any  one 

Fig.  20. 


of  the  chambers,  care  should  be  taken  to  open  the  valve-cock,  so 
as  to  afford  free  escape  to  the  confined  air. 


LABORATORY  JACK. 


49 


Fig.  21. 


When  the  still  is  to  be  an  independent  piece  of  apparatus,  it 
should  be  movable,  and  constructed  as  hereafter  described ;  but 
in  those  laboratories  provided  with  a  jack,  the  better  plan  is  to 
make  it  a  permanent  fixture,  and  so  arrange  it  as  to  make  it  use- 
ful either  with  the  naked  fire,  or  a  direct  current  of  wet  steam 
from  the  jack,  as  the  heating  medium.  Such  a  system,  combin- 
ing its  advantages  with  those  of  the  steam  series  and  the  jack 
itself,  will  render  the  laboratory  most  conveniently  and  economi- 
cally efficient  for  every  branch  of  chemical  pursuit. 

The  arrangement  best  suited  to  this  end,  is  shown  by  the  fore- 
going drawing,  Fig.  20.  The  whole  is  presented  in  front  view, 
just  as  it  appears  when  in  operation.  The  brickwork,  in  which  it 
is  set,  abuts  against  the  chimney  and  connects  with  the  flue  through 
the  furnace  of  the  still.  This  furnace,  instead  of  being  in  front, 
to  inconvenience  the  operator  with  its  heat  and  dust,  is  placed  at 
the  side  9r  right  end,  as  shown  by  Fig.  21,  the  lower  door  being, 
the  entrance  to  the  ash-pit,  and  the  upper  to 
the  furnace  or  fire-hole.  The  refrigerant  or 
cooling-tub  c,  has  its  position  to  the  left  of 
the  brickwork.  All  the  parts  are  drawn  to  a 
scale  of  one  inch  to  the  foot ;  and  their  proper 
shapes  are  shown  by  the  figures,  to  avoid  the 
necessity  of  elaborate  description. 

The  lower  portion  or  body  of  the  still  5, 
is  made  of  heavy  sheet  copper  tinned  inte- 
riorly. The  head  c  is  cast,  wholly,  from  pure 
block  tin.  Projecting  from  the  interior  of 
the'  still,  near  the  bottom,  is  a  tinned  copper  tube,  which  passes 
forwards  through  the  brickwork  and  ends  in  a  stop-cock  fixture, 
from  which  rises  a  glass  tube.  The  cock  serves  to  shut  off  com- 
munication between  the  still  and  tube,  as  may  be  necessary  in 
case  of  accident  to  the  latter ;  and  the  tube  itself,  graduated  into 
inches,  presents  a  scale  which  will  at  all  times  indicate  the  height 
of  liquid  in  the  still.  This  indicator  is  protected  by  a  half 
casing  of  metal,  in  which  it  rests  against  the  front  wall  of  the 
brickwork,  a  clamp  or  two  serving  to  keep  it  steady.  The  still 
has  two  supplementary  parts,  one  of  which  is  a  cullendered  lining 
of  block  tin,  shown  by  Fig.  22,  and  the  other  a  perforated  false 


50  LABORATOKY   JACK. 

bottom  of  the  same  material.     The 
Fig.  22.          firgt  is  made  to  fit  to  the  jnouth  Of 

the  still  in  such  a  manner  that  the 
same  head  will  adjust  with  both  the 
inner  and  outer  vessel  equally  well. 
The  latter  is  intended  as  a  support  for  organic 
or  other  matters  alterable  by  contact  with  highly 
heated  surfaces,  and  is  more  particularly  adapted  for  distillations 
with  the  naked  fire.  As  it  may  be  necessary  frequently  to  re- 
move this  bottom,  for  the  purpose  of  cleaning  it  or  dispensing 
with  its  use  in  some  operations,  it  is  constructed  of  two  parts, 
connected  by  hinges  in  the  centre,  so  as  to  form  a  fold  which  will 
pass  through  the  mouth  of  -the  still. 

The  block  tin  cullender,  shown  in  the  drawing  of  the  still  by 
dotted  lines,  is  designed  for  use  in  the  distillation  of  bulky  sub- 
stances, particularly  those  of  vegetable  origin,  by  a  direct  cur- 
rent of  wet  steam.  It  allows,  in  a  degree,  the  application  of  the 
displacement  principle  in  distillation,  for  as  the  current  of  steam 
enters,  it  passes  upwards  through  the  holes,  thence  through  the 
mass  of  matter  supported  in  the  cullender,  and  the  first  portion 
of  the  distillate  reaches  the  condenser  saturated  with  the  volatile 
parts  of  the  substance  under  treatment,  and  without  mixture  of 
any,  light,  solid  particles  driven  over  mechanically,  as  would 
otherwise  be  the  case.  The  process  effects  filtration  at  the  same 
time  that  it  constantly  renews  the  surface  of  the  solid  matter  to 
the  solvent  action  of  succeeding  relays  of  fresh  steam,  while  it 
also  affords  the  means  of  determining  when  the  former  is  ex- 
hausted, and  the  distillation  should  be  stopped. 

The  steam-pipe  is  introduced  through  the  opening  0,  and  leads 
to  within  an  inch  of  the  bottom,  where  it  takes  an  angular  bend 
and  ends  in  a  rose,  which  is  a  perforated  copper  ball  with  a  screw- 
cut  shoulder,  by  which  it  is  attached  to  the  steam-pipe.  The 
latter  is  so  adjusted  in  the  opening,  by  means  of  a  shoulder  and 
coupling-nut,  as  to  form  a  tight  joint.  When  the  still  is  to  be 
used  with  the  naked  fire  alone,  this  pipe  must  be  removed,  and 
the  opening  closed  with  a  screw-plug  provided  for  the  purpose. 
It  should  be  remarked,  that  .this  opening  serves  also  for  the  en- 
trance of  a  funnel-tube  through  which  to  introduce  fresh  addi- 
tions of  liquid  as  may  be  required  to  maintain  a  supply  in  the 


THE   STILL.  51 

still,  without  the  necessity  of  stopping  the  operation  or  removing 
the  head. 

The  distillate,  in  passing  from  the  still-head,  goes  into  the 
worm  firmly  fixed  in  a  cooler,  c.  The  worm  is  a  series  of  block 
tin  tubes,  as  shown  by  the  dotted  lines.  The  mouth  of  the  first 
joint  receives  the  beak  of  the  still-head,  and  that  of  the  last  joint 
empties,  through  a  bent  nozzle,  into  the  receiving  vessel,  gene- 
rally a  glass  or  stone  jar,  as  seen  at  d.  To  facilitate  the  cleans- 
ing of  the  joints,  they  are  fitted  at  the  ends  g  with  screw-plugs, 
which  being  removed,  allow  free  access  to  the  interior  with  a  cloth 
and  ramrod. 

The  cooler  is  made  of  galvanized  iron,  or,  still  better,  of  tinned 
copper ;  and  in  order  to  accommodate  the  long  joints  of  the  worm 
which  is  soldered  to  it,  its  form  is  oval.  The  pipe  through  which 
it  receives  cold  water  is  close  to  the  side,  and  extends  nearly  to 
the  bottom,  as  shown  at  s.  A  connection  with  the  hydrant  is 
made  by  a  branch-pipe  and  cock,  as  shown  at  m.  The  opening 
for  the  exit  of  the  warm  water  is  seen  at  #,  and  leads  into  another 
pipe  hj  running  down  the  outside  of  the  cooler  into  the  drain  or 
gutter.  A  cock  x  serves  fer  draining  off  sediment  as  it  accumu- 
lates by  deposition  from  the  water. 

We  have  left  the  framework  or  stand  open  in  the  drawings  for 
the  better  exhibition  of  the  different  parts  of  the  apparatus ;  but 
in  practice  it  must  be  closed,  so  as  to  circumscribe  the  radiated 
heat,  which  would  otherwise  escape  and  be  lost.  There  is,  how- 
ever, a  door  in  front  of  each  vessel  to  afford  access  within,  as 
may  be  necessary  for  occasional  inspection  of  the  valve-cock. 

The  description  of  this  apparatus  will,  itself,  afford  a  fair  idea 
of  the  great  convenience  of  its  several  parts.  Not  the  least  im- 
portant of  its  advantages  is  the  readiness  with  which  the  pieces 
may  be  adapted  to  so  many  uses.  Moreover,  deriving  its  steam 
from  the  jack,  which  is  always  in  operation,  no  fuel  or  time  are 
wasted  in  getting  it  ready  for  service.  It  gives,  too,  an  easily 
manageable  heat,  and  is  free  from  all  the  objections  to  a  naked 
fire,  particularly  in  the  treatment  of  many  vegetable  matters, 
which  are  easily  altered  by  the  action  of  the  latter. 

When  the  laboratory  is  not  provided  with  a  jack  or  steam- 
generator,  then  the  construction  of  the  still  must  be  somewhat 
different,  and  its  position  may  be  to  the  left  of  the  furnace,  as  at 


52 


THE   STILL. 


Fig.  24. 


E  H,  PI.  2.  It  should  combine  the  double  advantage  of  an  adap- 
tation to  the  heat  of  a  direct  fire,  or  that  of  a  water-bath ;  and 
to  economize  room,  it  must  be  compact  and  movable,  and  there- 
fore is  set  in  a  heavy,  stove-like  cylinder  of  sheet  iron  as  a  sub- 
stitute for  brickwork.  The  fire-door  is  as  shown  in  the  figures 
be'low,  and  in  order  to  prevent  the  overheating  of  the  iron  cylin- 
der, the  part  which  contains  the  fire  should  be  lined  with  a  re- 
fractory earthen  cylinder,  of  about  two  inches  thickness,  as  at  b 
and  c,  in  Fig.  24.  The  smoke-pipe  leads  into  the  circular  open- 
ing of  the  opposite  flue.  The 
body  of  the  still  rests  upon 
the  rim  of  this  furnace  at  #, 
by  its  flange,  which  surrounds 
it  immediately  below  its  han- 
dles. It  is  shown  by  C,  Fig. 
25.  Its  dimensions  should 
be  so  much  less  than  those  of 
the  furnace,  as  to  leave  suffi- 
cient heating  space  around  its 
sides  and  bottom.  The  ma- 
terial of  the  still  is  copper,  and  the  joints  are  rounded  so  as  to 

Fig.  25.  Fig.  26. 


give  every  facility  in  cleansing.  Moreover,  round  edges  are  less 
liable  to  become  bruised  than  the  angular.  For  the  distillation 
of  substances  indestructible  at  high  temperatures,  this  still  is  ap- 
plicable over  the  naked  fire,  but  for  more  alterable  bodies,  the 
intervention  of  water  is  necessary,  and  so,  accordingly,  an  inner 
tinned  copper  or  enamelled  iron  jacket  is  provided.  The  form 


THE   STILL.  53 

and  position  of  this  jacket  are  shown  at  B,  by  the  dotted  lines  in 
Fig.  25.  It  is  a  straight  cylinder  with  convex  bottom,  and  a 
broad  rim,  serving  also  as  a  flange  or  rim  for  its  support  in  the 
still.  Its  dimensions  are  four  inches  in  diameter  and  eight  inches 
in  depth  less  than  those  of  the  still.  The  head  or  capital,  which 
should  be  of  tinned  copper,  or,  preferably,  of  pewter,  is  shown 
at  B.  The  rim  is  made  to  fit  the  mouth  of  either  the  still  or 
water-bath,  and  hence  the  same  head  answers  in  both  naked  and 
bath  distillations.  The  beak  conveys  the  vapors  accumulating  in 
the  capital,  into  the  refrigerant  or  condenser,  which  consists  of  a 
pewter  worm,  Fig.  26,  encased  in  a  wooden  tub  kept  constantly 
supplied  with  cool  water  through  the  pipe  e.  The  water-pipe, 
which  carries  off  the  heated  water  displaced  by  the  cold  water, 
runs  from  the  top  of  the  tub  and  has  its  exit  into  the  sink,  or 
through  the  wall,  into  the  gutter.  These  two  pipes  are  better  of 
lead.  The  vapors  in  passing  through  the  worm  are  condensed, 
and  drop  as  a  liquid  into  a  receiver,  which  is  placed  beneath  the 
outlet  pipe  near  the  bottom  of  the  tub. 

To  convert  the  apparatus  into  a  water-bath  (for  in  many  dis- 
tillations the  temperature  must  not  exceed  the  boiling-point  of 
water  or  a  saline  solution),  it  is  only  necessary  to  charge  the 
outer  jacket,  or  still,  with  the  proper  quantity  of  liquid,  and 
then  to  insert  the  inner  casing  B,  which  slides  into  the  mouth 
and  fits  tightly. 

In  the  distillation  of  flowers,  roots,  and  other  substances,  in 
the  naked  still,  a  too  close  contact  with  its  heated  sides  and 
bottom  renders  them  liable  to  injury  by  scorching,  and  therefore 
it  is  necessary  to  have  a  strong  wire  stand 
with  one   or   two   cullendered   shelves  upon  Fig.  27. 

which  to  place  the  material.     The  lower  shelf 
h  being  an  inch  or  two  from  the  bottom  of  the 
still,  prevents  all  liability  of  contact  between 
it  and  the  material.     This  apparatus  is  shown 
by  Fig.  27.     When  the  still  is  not  in  use  for 
its  legitimate  purpose,  by  removal  of  the  wire  shelving,  it  be- 
comes  an   excellent   kettle   for    any   of  the   ordinary   boiling 
operations. 

In  the  blank  space  of  the  wall  to  the  left  of  the  front  entrance, 
stands  a  deal  wood  cask,  with  wooden  spigot,  mounted  upon  a 


54 


THE   LABORATORY — THE   SINK. 


stand  of  convenient  height.  This  serves  as  a  reservoir  for  dis- 
tilled water,  and  the  opening  in  the  top,  for  pouring  in  the  water, 
must  be  kept  tightly  closed  to  prevent  the  admission  of  dust  or 
absorption  of  gases. 

Fig.  28. 


Beindroffs  Apparatus. — This  utensil,  Fig.  28,  is  not  suited  for 
very  large  operations,  but,  being  compact  and  convenient  in 
arrangement,  will  answer  admirably  for  small  laboratories.  It 
combines  many  of  the  conveniences  of  the  jack,  and  most  of  the 
requisites  for  general  furnace  business,  such  as  digesting,  distil- 
ling, macerating,  boiling,  decocting,  dissolving,  and  evaporating. 


THE   LABORATORY — GAS   CHAMBER.  55 

The  whole  is  set  in  brickwork  against  a  chimney-flue,  and  occu- 
pies a  space  of  about  four  square  feet.  There  is  a  furnace  and 
grate  in  the  brickwork  for  heating  it  by  the  naked  fire  when 
necessary;  but  there  are  arrangements,  also,  for  the  use  of  steam. 

The  framework  is  of  copper,  and  constructed  so  as  to  act  the 
double  part  of  a  boiler  and  a  support  for  the  smaller  pieces  of 
apparatus.  To  this  end  it  is  studded  throughout  with  circular 
openings  of  different  sizes,  which  are,  severally,  receptacles  for  a 
tinned  copper  still,  a  tinned  copper  evaporating  pan,  a  porcelain 
and  wedgwood  capsule,  a  block  tin  digesting  cup,  and  two  other 
digesting  cups  of  copper,  lined  respectively  with  glass  and  cop- 
per. There  is  also  a  hole  for  a  steam-funnel  for  the  support 
of  retorts,  dishes,  &c.,  when  a  steam  bath  is  desirable.  All 
these  vessels  are  surrounded  by  the  boiler,  which  imparts  to 
them  its  heat ;  and  a  small  screw-plug  in  the  top  of  the  boiler 
serves  as  a  connection  for  a  steam-pipe,  as  may  be  desirable. 
The  height  of  the  water  in  the  boiler  is  indicated  by  a  glass  tube 
properly  affixed.  A  block  tin  worm  or  condenser  and  a  cooling- 
tub  are  also  accompaniments  for  the  still,  and  to  add  still  more 
to  the  efficiency  of  the  apparatus  there  is  a  sand-bath  on  the  top 
and  a  drying-chamber  at  the  side. 

G-as  Chamber. — This  is  a  very  necessary  appointment  of  every 
laboratory,  as  there  are  many  operations  which,  in  >  the  cold,  give 
off  unwholesome  vapors  that  should  be  excluded  from  the  work- 
ing apartment,  and  must,  therefore,  be  conducted  under  cover; 
such,  for  example,  as  processes  requiring  the  use  of  sulphuretted 
hydrogen,  carbonic  acid,  and  other  gases  deleterious  in  their 
effects  upon  the  system  or  discomforting  to  the  operator.  The 
proper  arrangement  is 'a  close  framework  set  into  the  wall  against 
a  chimney-flue,  or  in  such  a  position  that  a  pipe  leading  from 
it  may  readily  communicate  with  a  neighboring  flue.  A  dove- 
tailed window  frame,  divided  midway  by  a  strong  and  level  shelf, 
will  be  appropriate  for  the  purpose.  It  should  have  a  height  of 
six  feet,  a  width  of  three  feet,  and  a  depth  of  sixteen  inches. 
Four  inches  of  the  depth  should  be  imbedded  in  the  wall,  and  to 
insure  perfect  tightness,  the  joints  should  be  closed  with  plaster. 
The  part  above  the  shelf  is  a  common  glazed  sash  hung  with 
counterpoise  weights,  to  afford  facility  of  access  and  for  viewing 
the  interior  during  the  progress  of  operations,  without  the  neces- 


56 


THE   LABORATORY — THE  SINK. 


sity  of  raising  the  window.  The  shelf  is  the  table  upon  which 
the  apparatus  rests  when  in  operation,  and  immediately  below  it 
is  a  range  of  small  drawers  for  containing  matters  pertaining  to 
the  business  of  the  chamber.  The  space  beneath  the  drawers 
is  divided  down  the  centre  and  fitted  with  shelves  and  doors,  so 
as  to  form  a  closet  for  storing  the  apparatus  which  may  be  needed 
for  use  in  the  chamber.  The  annexed  drawing,  Pig.  29,  presents 

Fig.  29. 


an  intelligible  view  of  the  structure.  It  is  necessary  to  add  that 
the  noxious  emanations  find  vent  as  they  rise,  through  a  perfo- 
rated valve  let  into  the  chimney  after  the  manner  described  at 
p.  19. 

,  The  Sink. — In  the  corner  of  the  room  to  the  right  of  the 
refrigerant,  is  the  sink.  Its  position  will  be  better  understood  by 
reference  to  I,  PI.  2.  As  it  is  necessary  that  the  laboratory 
should  be  abundantly  and  constantly  supplied  with  water  for 
cleansing,  distilling,  and  many  other  operations,  it  is  better,  in 
those  cities  where  the  water  is  supplied  by  public  water-works,  to 


THE   LABORATORY — THE   SINK.  57 

make  an  attachment  to  the  main  conduit,  and  lead  the  water 
through  a  lead  pipe  directly  into  the  laboratory,  and  immediately 
over  the  sink.  The  only  arrangement  necessary  is  a  stop-cock 
at  the  termination  of  the  pipe,  to  regulate  the  flow  of  water. 
Fig.  30  represents  a  sink  thus  arranged.  The  trough  may  be  of 
wood  and  lined  with  sheet  lead,  which  metal  is  preferable  to 


Fig.  30. 


Fig.  31. 


zinc,  because  less  liable  to  corrosion  by 
acids.  It  would  be  much  better,  however, 
to  have  it  constructed  wholly  of  soap- 
stone,  as  this  material  possesses  all  the 
necessary  qualities.  The  floor  beneath, 
to  a  certain  extent  around  the  sink,  should 
also  be  covered  with  sheet  lead,  otherwise 
its  continual  dampness  from  the  splash- 
ing water  would  endanger  the  health  of 
the  operator.  When  the  introduction  of 

water  by  conduit  is  impossible,  it  is  necessary  to  erect  immedi- 
ately over  the  sink  a  strong  iron-bound  oaken  reservoir  with 
cover,  which  must  be  daily  filled  with  buckets  from  the  neigh- 
boring pump.  In  either  case,  the  exit-cock  should  be  fitted  with 
a  diaphragm  filter,  Fig.  31,  containing  a  stratum  of  crushed 
quartz,  which  arrests  the  suspended  impurities  of  the  water 
during  its  percolation  through.  If  it  is  not  convenient  to  pro- 
vide one  of  the  above  filters,  an  economical  but  slower  and  less 
convenient  one  can  be  made  of  a  common  red  earthenware 
flower-pot,  by  covering  its  bottom  interiorly  with  a  linen  cloth 
and  filling  it  with  coarse  white  sand.  The  waste-pipe,  which 
must  be  constructed  so  as  to  admit  of  the  free  discharge  of  the 
waste-water,  is  led,  by  a  gradual  descent,  into  a  drain,  which 
conveys  its  charge  into  cess-pools  or  tanks  lined  with  bricks,  and 
sunk  into  the  ground.  As  the  emanations  of  foul  air  from  these 
pools  are  noxious,  they  should  be  placed  some  distance  from  the 
building,  and  kept  well  covered.  If  the  situation  be  favorable, 
the  drains  should  empty  themselves  into  a  gutter  or  some  running 


58 


THE   LABORATORY — CLEANSING   APPARATUS. 


Fig.  32. 


stream,  which,  in  conducting  away  the  foul  matter,  would  relieve 
the  air  of  the  apartments  of  its  noxious  effluvia. 

The  mouth  of  the  discharge-pipe  must  be 
fitted  with  a  cullendered  plug  (Fig.  32)  to  ar- 
rest the  passage  of  solid  matters,  which,  other- 
wise, would  fall  in  and  prevent  the  egress  of 
the  waste  waters. 

As  all  the  cleansing  operations  are  per- 
formed at  the  sink,  it  is  necessary  that  it  should  be  fitted  with 
several  shelves,  in  addition  to  those  which  may  be  arranged  by 
its  sides.  To  afford  free  escape  to  the  draining  water,  those 


Fig.  33. 


Fig.  34. 


which  are  to  hold  the  glass-ware  had  better  be 

cullendered;  and  upon  one,  for  the  safety  of  the 

test-tubes  and  other  hollow  apparatus  of  too  small 

circumference  to  stand  upright  alone,  there  should 

be  a  series  of  draining-pins,  as  shown  by  Fig;  33. 

A  rack  of  horizontal  pegs,  for  draining  retorts  and 

other  irregular-shaped   apparatus,  might   also  be 

conveniently  arranged  upon  a  part  of  the  space. 

For  draining  vials  and  small  flasks,  an  upright 

stand  fitted  with  pegs,  as  shown  in  Fig.  34,  is  perhaps  preferable 

to  the  horizontal  rack. 

A  jar  of  soft  and  a  piece  of  Castile  soap  should  have  appro- 
priate places  in  the  vicinity  of  the  sink ;  and  near  by  also,  say 
on  the  back  of  the  door,  for  the  sake  of  economizing  room,  there 
must  be  two  long  towels  hung  on  rollers,  as  at  Fig.  35.  One  of 
these  towels  is  exclusively  for  the  hands, 
the  other  for  drying  the  cleansed  glass- 
ware, &c.  The  other  accompaniments  to 
the  sink  are  a  coarse  towel,  a  small  paint- 
brush, a  bottle  of  shot,  a  series  of  wires, 
some  tow  and  raw  cotton,  and  a  wire  in- 
strument for  the  removal  of  corks  from 


Fig.  35. 


THE  LABORATORY — CLEANSING  APPARATUS, 


59 


Fig.  36. 

O 


the  interior  of  bottles.  This  latter  is  nothing  more  than  three 
plies  of  stiff  wire  united  together  at  their  upper  ends,  and  bent 
in  angular  forms  at  their  lower  ends.  A  hair  brush, 
like  that  shown  by  Fig.  36,  for  cleansing  the  sides 
of  test  tubes  and  cylindrical  vessels,  should  also  be 
provided.  The  paint-brush  is  for  washing  out  wide- 
mouthed  apparatus,  and  can  be  well  substituted  by  a 
mop  or  twine-brush  of  similar  shape,  and  much  used 
in  housewifery  for  washing  tea-china.  These  and  the 
cork-wires  are  to  be  had  at  any  house-furnishing  esta- 
blishment. 

Of  the  series  of  wires,  one  should  be  stiff  and  skewer- 
like,  with  pointed  end,  to  remove  those  particles  of  dirt, 
tenaciously  adhering  to  bottles,  which  have  resisted 
the  cleansing  action  of  agitation  with  sand  or  gravel. 
The  remaining  wires  may  be  of  stiff  iron  and  rough- 
ened, or  jagged  at  the  ends,  in  order  the  more  securely 
to  prevent  the  slipping  of  the  tow  or  cotton,  which  is 
wrapped  and  tied  thereon  to  facilitate  the  cleansing  of 
the  glasses.  The  tow  or  cotton  is  to  be  renewed  as 
frequently  as  is  necessary  to  cleanliness.  A  portion 
of  the  wires  may  be  from  J  to  J  of  an  inch  thick,  and 
16  to  18  inches  long.  The  rest  for  smaller  apparatus 
may  be  of  proportionably  less  dimensions.  Several 
long  wedge-shaped  oaken  sticks  are  also  convenient  for  more 
effectually  applying  the  cloth  or  towel,  with  which  they  are  tem- 
porarily wrapped,  to  the  angular  spaces  at  the  bottom  of  the 
glasses.  For  long  tubes,  flasks,  and  deep  bottles,  a  ramrod  with 
its  screw  end  is  a  most  efficient  cleansing  instrument,  as  it  takes 
a  tight  hold  of  the  cotton  or  cleansing  rag  and  may  be  very  dex- 
terously handled.  All  of  these  pieces  of  apparatus  should  have 
appropriate  places  near  to  the  sink.  Pegs  or  nails  are  very  con- 
venient hangers,  and  two  or  four  cuddies  or  drawers  make  ser- 
viceable receptacles  for  the  tow,  cotton,  and  rags. 

In  those  situations  where  it  is  not  convenient  to  introduce  the 
water  through  a  pipe,  there  must  be  erected  immediately  over 
the  sink  a  strongly  braced  shelf,  as  a  support  to  a  closely  covered 
deal-wood  cistern  for  the  reception  of  water.  The  water  is  sup- 
plied either  by  bucketfuls  from  a  neighboring  pump,  or  else  is 


60 


THE   LABORATORY — THE   TOOL-CHEST. 


Fig.  37. 


pumped  in.     In  the  former  case,  the  position  of  the  sink  in  the 
corner,  and  near  to  the  door,  allows  great  facility  in  filling  it. 

Next  to  the  sink,  occupying  the  inner  wall-spaces  on  either 
side  of  the  door,  as  at  m  m,  PL  2,  are  strong  shelving  cuddies, 
racks,  and  pegs,  as  receptacles  for  crucibles,  furnaces,  iron  pots, 
pans,  lead  coils,  and  other  apparatus  needful  in  the  processes  and 
operations  performed  in  the  room. 

The  corner  shelves  K,  PL  2,  strongly  built,  are  for  the  re- 
ception of  the  larger  pieces  of  apparatus.  There  should  also 
be  reserved  a  wall  space  for  the  still,  generator,  &c.,  when  out 
of  use. 

The  anvil  occupying  the  position  L,  Plate  2,  and  resting  upon 
a  foot-block,  is  a  most  useful  implement,  and  a  necessary  accom- 
paniment to  the  tool-chest,  upon  the  opposite  side  of  the  room, 
at  w,  PL  2.     This  tool-chest,  which  is  shown  by  Fig.  37,  com- 
bines in  its  construction  the 
conveniences     of    a     work- 
bench.    The  vice  is  affixed 
towards  the   end,   so   as   to 
give  full  working  room.    The 
drawers  are  receptacles  for 
the   requisite    tools,    among 
which  should  be  a  hammer, 

hatchet,  saw,  a  chisel  of  each  kind,  gimlets,  awls,  files  of  the 
various  shapes,  pincers,  a  soldering  iron,  a  screw-driver,  with  an 
assortment  of  screws,  nails,  &c.  A  glue-pot  will  also  be  found  a 
necessary  addendum.  The  bench  should  be  about  four  feet  in 
length,  and  of  height  suitable  to  the  comfort  and  convenience  of 
the  operator. 

The  pedestal  0,  PL  2,  occupying  the  space  between  the  door 
and  left  front  window,  supports  a  pear-shaped  reservoir  of  deal- 
wood,  or  preferably  of  blue  stone,  for  the  reception  of  distilled 
water,  a  supply  of  which  should  be  constantly  kept  on  hand. 

A  tin  match-box,  an  essential  requisite  of  the  furnace-room, 
should  have  a  dry  position  in  some  convenient  place  upon  the 
wall. 

The  charcoal,  coke,  and  sand  can  either  be  kept  in  the  cellar, 
or  else  in  bins  occupying  the  base  of  the  shelving,  and  resting 
immediately  upon  the  floor. 


H 


© 


THE  LABORATORY — THE  OPERATING-ROOM. 


61 


A  solid  oaken  pedestal  for  the  iron  mortar,  and  several  wooden 
buckets  for  general  convenience,  are  also  necessary  pieces  of 
furniture. 

All  operations  emitting  corrosive  or  disagreeable  vapors  should 
be  confined,  as  far  as  possible,  to  this  room.  In  passing  sulphur- 
etted hydrogen,  chlorine,  or  sulphurous  acid  through  liquids,  the 
vessels  should  rest  either  upon  a  shelf  projecting  out  of  the 
window,  or  else  under  a  hood  which  can  carry  the  emanations 
into  the  flues,  and  thus  prevent  much  corrosion  of  apparatus  and 
discomfort  to  the  operator. 


CHAPTER  IV. 


Fig.  38. 


THE   OPERATING-KOOM. 

BETWEEN  the  office  and  the  furnace-room,  and  occupying  the 
whole  residual  floor-space  C,  PI.  2,  of  the  apartment,  is  the  main 
operating-room  (PI.  1),  of  dimensions  on  the  plan,  24  by  18-6 
feet.  In  this  room  are  performed  all  the  more  delicate  manipu- 
lations of  analysis  and  experimental  research,  and  hence  the 
necessity  of  great  cleanliness.  The  prescribed  arrangement 
frees  it  entirely  from  the  dust 
of  the  coarser  operations  of  the 
furnace-room  (the  door  of  which 
should  be  kept  constantly  closed), 
while  the  perforated  register, 
before  recommended,  and  coun- 
terpoised windows,  of  adequate 
dimensions  to  afford  abundant 
light,  promote  thorough  ventila- 
tion. In  this  room  is  stored 
nearly  all  the  finer  apparatus 
and  materials.  The  main  fea- 
ture of  the  apartment  is  the 
operating-table,  which  is  shown  by  Fig.  38.  Its  position  (M,  PI. 
2)  is  against  the  front  wall-space  between  the  middle  and  left 
window.  It  may  be  constructed  of  pine  wood,  though  cherry  or 


62        THE  LABORATORY — THE  OPERATING-TABLE. 

walnut  is  preferable.  At  all  events,  the  top,  which  must  project 
over  all  around  2  inches,  should  be  either  of  these  woods  or  ash, 
and  at  least  of  an  inch  thickness ;  glued  at  the  grooves,  and 
grooved  and  clamped  at  the  cross-grained  end,  so  as  to  prevent 
warping  or  shrinking,  either  of  which  creates  a  great  inconveni- 
ence to  the  operator.  It  is  indispensable  that  the  stuff  be  old,  well 
seasoned  and  joined,  because  any  shrinking  will  form  cracks  and 
crevices  for  leakings  to  penetrate  into  the  drawers  beneath,  and 
injure  their  contents.  When  the  top  is  made  of  common  wood, 
it  should  be  covered  with  india-rubber  cloth,  drawn  tightly  over, 
and  fastened  under  the  edges  by  copper  nails.  The  height  of 
the  table  proper  is  3  feet.  Depth  2  feet  4  inches.  The  length 
of  the  top  is  5  feet.  The  shelf-stand  or  test-case,  which  slides 
in  grooves,  and  is  fastened  to  the  top  of  the  table  by  screws,  is 
30  inches  in  length,  and  30  to  32  in  height.  The  distance 
between  the  shelving  is  unequal,  in  order  to  accommodate  the 
different  sized  bottles.  The  space  between  the  lower  and  first 
shelf  may  be  7J  inches,  diminishing  gradually  upward,  so  that 
the  interval  between  the  top  and  topmost  shelf  shall  not  be 
greater  than  5  inches.  The  shelves  may  be  of  light  stuff,  say  f 
inch  thickness.  To  protect  the  bottles  from  dust,  the  test-case 
should  have  a  glass  front,  hung  with  counterpoise  weights  in  the 
manner  of  a  window  sash,  so  as  to  afford  facility  in  raising  and 
lowering  it.  The  upper  drawers  should  have  a  depth  of  2J 
inches ;  the  lower  3 \  inches.  The  closets  below  should  be  fitted, 
the  one  on  the  right,  with  movable  shelves,  the  other  on  the  left 
with  rows  of  wooden  pegs,  obliquely  hung. 

All  the  knobs  should  be  of  that  kind  known  as  "  "White  Ar- 
gillo"  both  on  account  of  their  durability  and  neat  appearance. 

This  table  thus  constructed  is  the  operating-table  of  the 
experimenter,  and  must  be  furnished  with  such  apparatus  and 
materials  as  are  in  constant  requisition,  and  hence  the  conve- 
nience of  the  shelving,  drawers,  and  pegs,  as  their  receptacles. 
As  it  is  desirable  that  the  table  should  not  be  encumbered  with 
apparatus  in  unnecessary  amount,  only  those  pieces  which  are  of 
constant  use,  and  required  to  be  at  hand,  should  find  an  abode 
within  the  limits  of  this  table.  The  general  supplies  of  the 
laboratory  are  stored  elsewhere,  as  will  be  directed  hereafter. 


THE  LABORATORY — THE  OPERATING-TABLE. 


63 


One  of  the  upper  drawers  should  be  reserved  for  filters,  of  the 
different  kinds  of  paper  used  for  the  purpose.  These  may  be 
purchased,  already  cut,  and  of  the  different  sizes,  neatly  put  up 
in  boxes.  If  they  are  made  in  the  laboratory,  it  is  necessary  to 
have  a  series  of  circular  tins,  corresponding  with  the  size  of  the 
funnels  most  in  use,  by  which  to  shape  them. 

Another  drawer  may  be  reserved  for  small  tubes,  rods,  pipettes, 
and  glass  or  porcelain  connections.  Another  for  platinum  cru- 
cibles, spatulas,  and  fine  metallic  vessels. 

The  small  retorts,  bulbs,  and  the  like,  should  also  have  an 
appropriate  drawer.  The  larger  retorts  and  glass  apparatus  find 
appropriate  places  in  the  cupboards. 

The  top  drawer  to  the  extreme  right  should  be  fitted  up  in 
desk-form,  and  furnished  with  pen,  ink,  and  paper,  for  the  con- 
venience of  making  rough  notes  during  operations,  which  are 
afterwards  to  be  neatly  transcribed  in  a  note-book,  or  "  Record 
of  Laboratory  Operations,"  kept  especially  for  the  purpose  in 
an  appropriate  place  in  the  office  desk.  The  valuable  infor- 
mation which  can  in  this  way  be  stored  up,  in  a  short  time, 
amounts  to  a  vast  fund,  and  will  serve,  to  the  great  convenience 
of  the  writer,  as  a  remembrancer  of  facts  acquired  and  of  errors 
avoided.  A  coarse  towel  should  always  be  an  accompaniment  to 
this  table,  and  have  a  hanging  position  at  its  side. 

The  two  lower  drawers  beneath  the  closets  may  be  reserved 
for  the  more  weighty  implements. 

A  leaden  funnel,  supported  by  a  wooden  casing,  with  its  barrel 

Fig.  39, 


united  to  a  leaden  pipe  leading  through  the  floor  into  the  street 


64 


THE   LABORATORY — THE   SPIRIT-LAMP. 


Fig.  40. 


gutter,  and  placed  immediately  to  the  right  of  the  table,  would 
be  very  convenient  for  receiving  and  conveying  off  the  slops  from 
the  test-tubes.  When  this  arrangement  is  not  practicable,  a 
bucket  of  india-rubber  must  be  substituted ;  for  the  practice  of 
emptying  test-tubes  upon  the  floor  is  slovenly  and  reprehensible, 
and  by  keeping  it  constantly  damp,  the  comfort  of  the  operator 
is  greatly  disturbed. 

A  rack  with  test-tubes,  Fig.  39,  may  be  considered  one  of  the 
fixtures  of  the  operating-table. 

The  spirit-lamp  which  furnishes  the 
heat  for  table  operations,  and  is  shown 
by  Fig.  40,  will  be  spoken  of  more  fully 
hereafter.  When  coal  gas  can  be  com- 
manded, it  is  far  more  convenient  and 
economical,  and  by  a  particular  arrange- 
ment, may  be  made  to  yield  heat  enough 
for  evaporation  and  ebullition  in  capsules, 
and  the  different  operations  of  digesting 
in  bell  glasses,  &c.  By  the  use  of  a  large 
Argand  burner  fixed  over  the  jet  of  the 
table  blow-pipe,  we  can  obtain  the  power 
of  a  blast.  The  admixture  of  the  gas,  in 
this  way,  with  atmospheric  air,  increases 
the  heat  to  such  an  extent  as  to  allow  the 
ignition  of  precipitates  in  crucibles,  and 
the  accomplishment  of  many  other  minor 

operations,  which  formerly  required  the  use  of  a  furnace.     The 

arrangement  by  which  these 
results  are  attained,  so  as  to 
avoid  entirely  the  deposition 
of  carbon  on  the  bottoms  of 
the  vessels,  is  shown  by  Fig. 
41.  B  is  a  cylinder  of  sheet 
copper,  stretched  over  the  top 
of  which,  and  fastened  by  an 
iron  hoop,  is  a  fine  wire  gauze, 
covered  with  fine  gravel  to 
protect  it  from  wear  and 


Fig.  41. 


THE  LABORATORY — THE  GAS  FURNACE.         65 

tear.  In  order  to  promote  a  more  thorough  admixture  of  the 
gas  and  atmospheric  air  (which  is  effected  in  the  chimney),  there 
is  a  coarse  wire  gauze  diaphragm  c.  The  flexible  gas-pipe  of 
vulcanized  india-rubber  depending  from,  and  connected  by  a  gal- 
lows screw  A,  with  the  permanent  hanger  0,  terminates  in  an 
argand  burner  d.  To  prevent  a  scorching  of  the  table,  the 
burner  and  cylinder  both  rest  upon  a  thick  metallic  foot.  The 
air  enters  through  the  openings  in  the  lower  circumference,  being 
drawn  up  by  the  upward  current  of  gas,  which  is  let  on  and 
regulated  by  the  stop-cock  r\  and  the  mixture  thus  formed 
passing  through  the  upper  fine  wire  gauze,  above  which  it  is 
ignited,  should  burn  with  a  bluish  flame. 

"  Where  the  quantity  of  gas  is  too  great  for  the  amount  of  air 
admitted,  the  flame  will  be  white  and  smoky,  but  by  regulating 
the  supply  of  gas,  the  due  proportion  for  a  blue  flame  may  be 
easily  attained.  To  obtain  a  blue  flame  from  a  cylinder  of  large 
diameter,  a  considerable  quantity  of  gas  will  be  requisite,  and 
hence  an  economical  advantage  is  gained  by  employing  cylinders 
of  different  diameters.  In  the  same  cylinder,  also,  where  dif- 
ferent quantities  of  heat  are  desired,  the  lower  series  of  holes 
may  be  made  large,  and  a  ring  of  sheet-iron  slid  over  them,  by 
which  the  quantity  of  air  admitted  may  be  regulated  according 
to  the  quantity  of  gas  consumed.  The  cylinders  may  be  2J  to 
5  inches  diameter  by  6 — 8  inches  in  height ;  but  by  introducing 
several  pieces  of  coarse  gauze  <?,  at  short  distances  apart,  the 
height  may  be  diminished.  The  highest  amount  of  heat  produced 
by  this  apparatus  is  a  cherry-red  by  daylight.  For  burning  off 
filters  in  a  platinum  crucible,  a  cylinder  of  2J  inches  diameter  is 
amply  sufficient ;  but  for  heating  larger  vessels,  such  as  capsules, 
those  of  4 — 5  inches  diameter  are  desirable.  This  mode  of 
burning  the  gas  presents  the  advantages  of  producing  any  de- 
gree of  heat  as  high  as  a  red,  of  not  blackening  vessels  im- 
mersed in  the  flame,  and  of  avoiding,  with  more  certainty,  the 
fracture  of  porcelain  or  glass  vessels,  from  the  diffusive  character 
of  the  flame." 

The  ring  n,  sliding  upon  the  rod  of  the  upright  stand  A, 
serves  as  a  support  for  a  retort,  capsule,  or  crucible.  A  second 
chimney  g  placed  over  the  crucible  creates  a  uniform  and  constant 
draught. 


66 


THE   LABORATORY — THE   TABLE   SAND-BATH. 


Fig.  42. 


Very  neat  gas  furnaces  are  made  by  W.  F.  Shaw,  Boston. 

Those  for  laboratory  purposes 
have  a  broad  base,  as  shown 
in  the  drawing — Fig.  42 — to 
steady  their  position  on  the 
table.  Surmounting  the  wire 
gauze  diaphragm  is  a  perforated 
cylinder,  with  large  openings 
near  its  top  circumference  for 
the  promotion  of  influent  air- 
currents.  These,  by  perfecting 
the  combustion  of  the  burning 
mixture  of  air  and  gas,  not  only 
increase  its  heating  power,  but 
prevent  all  smoke  and  odor.  It 
is  necessary  to  add,  that  the 
meshes  of  the  wire  gauze  should 
be  kept  clean  by  the  occasional  application  of  a  tooth-brush. 

The  whole  of  this  apparatus  is  movable,  and  when  the  space 
which  it  occupies  upon  the  table  is  required  for  other  purposes, 
it  is  only  necessary  to  disconnect  it  from  the  hanger,  and  place 
the  whole  aside,  to  be  as  readily  replaced  again  when  wanted. 

The  introduction  of  gas  into  the  room  also  allows  the  use  of  a 
convenient  table  sand-bath,  for  certain  operations  which  require 
the  constant  supervision  of  the  operator.  It  consists  of  a  copper 

Fig.  43. 


box  B,  eighteen  inches  long,  twelve  inches  wide,  and  six  inches 
deep.  The  top,  which  is  ledged,  projects  over  about  an  inch, 
and  forms  the  bed  for  the  sand.  The  door  <?,  having  a  small 
semicircular  opening  at  its  base,  is  for  the  entrance  of  the  gas 


THE  LABORATORY — THE  CENTRE-TABLE. 


6T 


pipe  with  an  argand  burner  attached,  as  well  also  for  the  supply 
of  air  necessary  to  sustain  combustion.  The  fire  thus  applied 
heats  the  sand  on  the  top.  The  heated  air  has  an  exit  through 
the  circular  aperture  a,  after  having  traversed  the  interior,  which 
is  divided  lengthwise  by  the  partition,  as  represented  by  the 
dotted  lines.  The  communication  between  the  apartments  is  by 
an  opening  d,  in  the  diaphragm.  In  this  way  we  obtain  a  gradua- 
tion of  the  temperature  of  the  bath.  The  Swedish  chemists  im- 
prove upon  this  construction,  by  annexing  an  apartment  for  dry- 
ing filters  and  precipitates  as  well  as  for  keeping  liquids  hot  while 
filtering. 

These,  with  the  test-bottles  and  contents,  complete  the  para- 
phernalia of  the  operating-table,  and  so  we  proceed  to  describe 
the  next  most  important  piece  of  furniture  of  the  room. 

The  Centre  or  General  Table.— This  table  (N,  PL  2),  com- 
pactly fitted  to  serve  the  double  purpose  of  an  operating-table 

Fig.  44. 


for  distillations,  and  other  large  general  operations  of  the  labo- 
ratory which  would  occupy  too  much  room  upon  the  smaller 
table,  has  its  top,  also  of  cherry,  projecting  two  inches  all 
around,  and  grooved,  glued,  and  tightly  jointed,  as  directed  for 
the  preceding  table,  like  which,  its  lower  portions  may  also  be  of 
white  pine.  Its  proper  position  is  near  the  centre  of  the  room, 
so  as  to  afford  free  access  to  all  of  its  sides.  Fig.  44  gives  a 
view  of  it.  Its  dimensions  are  2-10  feet  height;  6-6  feet 
length ;  and  3-4  inches  breadth.  The  legs  are  fitted  to  a  bed, 
which  is  to  be  firmly  screwed  to  the  floor,  so  that  the  table  may 


68          THE  LABORATORY — THE  CENTRE-TABLE. 

be  stationary  and  firm,  as  any  jarring  may  create  serious  damage 
to  a  delicately  arranged  apparatus. 

The  drawer  space  should  not  exceed  15  inches  of  the  whole 
height  of  the  table.  The  end  drawers  are  necessarily,  from  the 
construction  of  the  table,  very  short,  and  may  be  omitted  en- 
tirely, though  it  is  better  policy  to  have  as  many  receptacles  as 
possible,  for  they  will  all  be  found  useful  as  well  as  convenient. 

Of  the  front  drawers,  one  should  be  appropriated  exclusively 
to  the  sheets  and  other  articles  of  india-rubber.  Accompanying 
these  must  also  be  a  pair  of  shears  and  a  ball  of  very  fine  linen 
twine  for  fashioning  and  securing  joints.  Another  drawer  must 
be  reserved  exclusively  for  the  corks  of  assorted  sizes.  Two 
smaller  apartments  or  divisions  are  also  necessary,  one  for  the 
files  of  different  sizes  and  shapes,  and  the  other  for  the  cork- 
presser,  and  borer,  of  which  more  will  be  said  hereafter. 

The  stock  of  filtering  paper  is  also  kept  in  another  of  these 
drawers ;  and  with  it,  the  circular  tins  by  which  it  is  cut  into 
different  sized  filters.  The  shears  for  cutting  the  paper  should 
be  kept  always  sharp  and  clean.  Another  drawer  divided  into 
compartments  is  required  for  the  reception  of  tow,  raw  cotton, 
bladders,  string,  &c. ;  and  another  for  the  clean  dusters  and 
towels  of  the  establishment. 

The  filtering-cloths  and  material  for  that  purpose  are  also  kept 
in  a  separate  drawer.  The  thermometers  and  hydrometers  are 
likewise  kept  in  a  distinct  drawer. 

There  are  many  other  articles  which  are  better  preserved  in 
drawers,  and  hence  there  is  a  necessity  for  the  whole  number  in 
the  table.  The  short  drawers  in  the  end  of  the  table  can  be  re- 
served for  minor  matters,  such  as  the  writing-diamond  and  similar 
implements. 

The  lower  bed  of  the  table  forms  an  excellent  shelf  for  the 
filter-stands,  retort-holders,  clamps,  supports,  and  other  wooden 
apparatus  in  frequent  use  upon  the  operating-table. 

All  the  irOn  stands  and  similar  apparatus  should  be  painted 
with  black  varnish,*  in  order  to  preserve  them  from  rust.  In 

*  To  fused  asphaltum,  40  ozs.  add  a  half  gallon  of  boiled  linseed  oil,  6  ozs. 
each  of  red  lead  and  litharge,  4  ozs.  dried  and  powdered  white  copperas.  Boil 
for  two  hours,  then  mix  in  8  ozs.  of  fused  dark  amber  gum,  and  a  pint  of  hot  lin- 
seed oil,  and  boil  again  for  two  hours  more.  When  the  mass  has  thickened,  with- 
draw the  heat  and  thin  down  with  a  gallon  of  turpentine. 


THE  LABORATORY — THE  PNEUMATIC  OR  BLAST  TABLE. 


69 


the  selection  of  iron  hollow-ware  for  purposes  of  ebullition  or 
evaporation,  that  which  is  lined  with  enamel  should  be  preferred, 
for  it  is  convenient,  readily  cleansed,  and  not  much  more  costly 
than  the  naked  iron  ware. 

The  mouth  blow-pipe  table,  occupying  a  position  against  the 
front  wall,  and  immediately  under  the  right  window,  as  shown  at 

Fig.  45. 


p,  PI.  2,  is  an  indispensable  piece  of  apparatus,  which  will  be  more 
fully  spoken  of  under  blow-pipe  operations. 

The  blast  or  pneumatic  table  (shown  in  position  at  ^,  PI.  2), 
which  is  sometimes  also  called  the  table  blow-pipe,  may  be  consi- 
dered as  an  implement  indispensable  to  the  chemist,  it  being 
alike  useful  for  bending  glass  tubes,  blowing  bulbs  and  other  small 
apparatus,  and  for  rapidly  effecting  the  decomposition  and  igni- 
tion of  substances,  which,  for  their  fusion,  would  require  an 
ordinary  wind  furnace.  The  most  convenient  form  of  this  appa- 
ratus is  shown  by  Fig.  45.  It  consists  of  a  brass  cylinder  piston 
2,  worked  by  a  treadle,  which  drives  the  air  into  a  large  tin  box 
enclosed  in  a  framework  1,  immediately  under  the  top  of  the 
table.  From  the  front  end  of  the  box  a  tube  rises 
through  the  table  top,  and  terminating  with  its 
small  jet  within  the  interior  of  an  Argand  burner, 
urges  the  air  directly  upwards,  producing  a  full 
flame.  The  Argand  burner  may  be  connected  with 
a  lamp  or  reservoir,  containing  a  solution  of  oil  of  turpentine,  or 
alcohol,  or  with  a  gas-pipe.  In  using  spirit,  the  burner  must  have 


Fig.  46. 


70  THE   LABORATORY — THE   AIR-PUMP. 

a  circular  wick  with  a  contrivance  for  adjusting  its  height.  Gas, 
however,  when  it  can  be  conveniently  obtained,  is  now  gene- 
rally used,  on  account  of  the  greater  power,  convenience,  and 
manageableness  of  its  flame.  An  approved  form  of  Argand 
burner,  for  laboratory  service,  is  shown  by  Fig.  46.  Being  con- 
structed with  a  porcelain  cap,  the  holes  through  which  the  gas 
arises  are  always  clean  and  free  from  stoppages  by  rust  or  other 
imperfections  incident  to  metal. 

Air-Pump. — The  small  table  at  r,  PI.  2,  is  used  for  the  air- 
pump,  which,  when  not  in  use,  should  be  kept  in  an  appropriate 
place  in  one  of  the  cases  in  the  balance-room.  Being  a  costly 
apparatus,  it  is  now  almost  exclusively  replaced  by  syringes, 
which  are  more  economical  and  not  much  less  convenient,  as 
made  for  the  purpose  at  the  present  time.  For  the  convenience 
of  uniformity,  the  attachment  screws  should  have  a  thread  similar 
to  that  of  the  stop-cock,  so  as  to  admit  of  a  ready  adaptation  to 
each  other  when  an  attachment  is  to  be  effected. 

The  Pneumatic  Syringe  is  a  very  serviceable  implement..  It 
serves  for  exhausting  air  from  the  various  forms  of  vessels  in 
numerous  experiments,  and  particularly  from  tubes  in  organic 
analyses  and  similar  operations.  It  is  also  useful  in  analyses,  for 
evaporations  and  dryings  under  an  exhausted  receiver  and  over 
sulphuric  acid,  or  other  hygroscopic  substance,  as  will  be  men- 
tioned hereafter,  under  the  proper  heads,  a  4-.^ 

To  preserve  the  efficiency  of  this  piece  of  apparatus  it  must  be 
frequently  worked,  and  to  prevent  leakage  at  the  joints,  the 
latter  as  well  as  the  piston  must  be  kept  well  oiled. 

Fig.  47. 


The  most  convenient  form  of  Pneumatic  Syringe  is  shown  in 
side  view  and  plan  by  Figs.  47  and  48.     When  in  use,  it  is  fast- 


THE  LABORATORY — THE  AIR-PUMP.  71 

ened  firmly  to  the  table  by  means  of  a  screw-clamp  made  ex- 
pressly for  the  purpose. 

The  base  A,  is  a  solid  piece  of  mahogany,  to  which  the  pump 
arrangement  is  firmly  attached  by  screws.  The  barrel  B,  9 
inches  long,  by  1J  inches  diameter,  is  of  brass,  and  carries  an 
air-tight  piston,  having  an  ordinary  silk  valve  opening  towards 
the  handle  L.  There  is  a  second  valve  also  at  K.  A  four-way 
cock  C,  allows  the  air  to  be  drawn  through  either  of  the  nozzles 
D  and  E ;  and  a  tube  F,  connects  this  cock  with  the  ground  glass 
bed-plate  G,  which  is  surmounted  by  a  glass  bell  receiver  H. 
The  edges  of  the  receiver  are  ground  perfectly  smooth  and  flat, 
and  should  be  greased,  so  that,  when  set  upon  the  bed-plate,  it 
may  form  an  air-tight  joint.  Connection  is  made  between  the 
receiver  and  atmosphere  by  means  of  a  cock,  I.  To  this  latter 
there  is  a  screw  adjustment  for  attaching  a  flexible  india-rubber 
tube  in  tube  manipulations. 

Fig.  48. 


The  construction  of  this  instrument  is  such  as  to  render  it  not 
only  efficient,  but  also  convenient  for  general  laboratory  purposes. 
Tubes  may  be  connected  at  either  end  of  the  cross-piece  D,  E,  as 
well  as  at  I;  and  the  bell  serves  for  all  the  analytic  operations  of 
drying  and  evaporating. 

The  table  s,  PI.  2,  to  the  right  of  the  air-pump,  is  a  stand  for 
the  common  scales  of  the  laboratory,  which  are  useful  for  testing 
the  weights  of  materials  purchased  and  for  weighing  coarser 
articles  in  large  quantities.  A  cheap  platform  balance  with  a 
movable  tin  dish  answers  conveniently  for  this  purpose.  The 
accompanying  (Avoirdupois)  set  of  weights  should  range  from  J 
oz.  to  8  Ibs. 

The  next  fixtures  to  be  described  are  the  cupboards.  Those 
affixed  to  the  partition  of  the  furnace-room,  as  at  t  and  uy  PL  2, 


•'•'•  £ 

72  THE  LABORATORY — THE  CUPBOARDS. 

are  more  properly  shelves,  with  curtains  instead  of  doors  to  pro- 
tect their  contents  from  the  dust.  The  set  t  may  be  occupied 
with  the  leaden  coils,  wooden  and  coarser  apparatus  of  the  apart- 
ment. The  curtains  of  common  muslin,  rendered  fire  proof  by 
immersion  in  a  solution  of  borax  and  sal  ammoniac,  and  drying, 
are  hung  by  means  of  small  brass  rings  upon  an  iron  rod  running 
the  whole  length  of  the  cap  of  the  shelving ;  and  in  order  to  keep 
them  distended,  leaden  bullets  should  be  sewed  at  occasional  dis- 
tances upon  the  lower  ends.  The  shelving  u  ascends  to  only  half 
the  height  of  that  of  £,  because  the  upper  space  js  to  be  reserved 
for  racks  and  rings.  The  shelves  are  intended  as  receptacles  for 
the  porcelain  capsules,  crucibles,  &c.,  the  bell,  beaker,  and  other 
similar  glass  apparatus,  care  being  always  taken  to  place  the 
larger  and  heavier  articles  upon  the  lower  shelves.  The  tube 
rack  is  nothing  more  than  a  series  of  pegs,  placed  closely  adjoin- 
ing in  a  straight  line  and  inclining  upwards,  so  as  to  prevent  the 
tubes  from  falling  through.  This  open  work  presents  the  whole 
stock  of  tubing  to  view  at  one  glance,  and  enables  a  ready  selection 
of  any  particular  piece  of  rod  or  tube.  The  smaller  pieces  which 
would  be  apt  to  fall  through,  should  be  kept  in  a  drawer  of  the 
centre-table  specially  appropriated  for  the  purpose.  The  remain- 
ing portion  of  the  upper  space  must  be  furnished  with  a  series  of 
various  sized  spikes  to  hold  retort  and  flask  rings.  These  rings, 
readily  made  of  wire,  vary  in  size  from  a  half  to  two  or  more 
inches  in  diameter,  and  receiving  the  necks  of  retorts  and  other 
curved  or  bent  apparatus,  retain  them  in  a  safe  and  convenient 
position.  The  rings  may  also  occupy  any  small  vacancies  upon 
the  walls  for  the  use  of  such  a  portion  of  the  apparatus  as  the 
cupboard  cannot  contain. 

The  small  cupboard  (v,  PI.  2)  in  the  corner  opposite,  may  be 
used  as  a  sort  of  general  cupboard  for  very  nice  little  matters, 
which  require  great  care  and  cleanliness  in  their  preservation. 
The  door  consequently  should  be  fitted  with  a  fastening  and  kept 
constantly  closed  when  not  in  use. 

The  cupboards  w  and  x  erected  against  the  part'tion  opposite, 
and  occupying  the  spaces  on  either  side  of  the  entrance  into  the 
office  are,  the  one  x  for  the  stock  of  drugs  and  chemicals ;  the 
other  w  for  the  new  empty  bottles,  to  be  confined  to  the  lower 
shelves,  and  for  the  specimens  that  may  from  time  to  time  be  ac- 


THE   LABORATORY — THE    BOTTLEF.  73 

cumulated  by  the  labors  of  the  operator.  The. lower  half  of  the 
cupboard  X  should  be  furnished  with  small  drawers  similar  to  a 
druggist's  case.  These  are  for  the  dye-woods,  sulphur,  chalk, 
and  other  similar  coarse  articles  of  stock,  which  are  more  securely 
kept  in  this  way  than  in  bundles,  which  are  liable  to  rupture  and 
damage  by  rough  handling  and  by  retaining  moisture.  The 
upper  shelving  is  to  be  exclusively  occupied  with  the  articles  in 
bottles,  which  are  to  be  arranged  in  classes,  the  compounds  of 
each  base  forming  a  class.  The  mineral  and  vegetable  acids  and 
organic  compounds,  have  also  each  a  separate  position.  The 
weightier  articles,  as  elsewhere  directed,  should  always  occupy 
the  lower  shelves,  both  for  convenience  of  handling  and  on  ac- 
count of  the  greater  stability  and  power  of  bearing  heavier 
weights  than  the  upper  shelves. 

The  "black-board,"  ?/,  PL  2,  made  of  artificial  slate,  is  hung 
sash-like  between  the  uprights  of  the  cupboard  w  and  x,  and, 
being  counterbalanced  by  weights,  can  be  lowered  or  raised  at 
will,  and  thus  leaves  free  access  to  the  office.  For  rough  calcu- 
lations and  plans,  drafts  of  apparatus,  diagrams,  &c.,  the  black- 
board is  very  convenient.  When  a  hand-slate  is  substituted,  the 
pencil  should  be  of  talc  (French  chalk)  which  makes  a  more  dis- 
tinct mark  than  the  common  slate-pencil,  and  gives  more  facility 
in  writing.  These  pencils  are  now  sold  in  most  of  the  stationery 
stores. 

Bottles. — Particular  regard  must  be  had  to  the  shape  and  ma- 
terial of  bottles  for  laboratory  use.  Those  intended  for  holding 
acids  or  salt  solutions,  must  be  of  well-annealed  glass,  which  is 
free  from  lead,  and  can  resist  the  corrosive  action  of  their  con- 
tents. Some  glasses,  containing  an  excess  of  alkali,  gradually 
lose  their  brilliancy  by  absorption  of  moisture  from  the  atmo- 
sphere ;  others  again  are  attacked  by  acid  and  alkaline  solu- 
tions ;  and  some,  indeed,  even  by  prolonged  contact  with  boiling 
water. 

The  inalterability  of  glass  by  air  or  chemical  agents  (hydro- 
fluoric acid  excepted)  is  proportional  to  its  hardness  and  infusi- 
bility.  Flint  glass  is  the  most  brilliant  and  comparatively  fusible, 
and  its  consequent  pliability  renders  it  available  for  thermometer 
and  barometer  tubes,  but  as  material  for  chemical  vessels  it  is 
far  inferior  to  the  Bohemian  glass  (a  silicate  of  potassa  and  lime, 


74 


THE    LABORATORY — THE   BOTTLES. 


with  large  traces  of  alumina),  which  is  harder,  lighter,  and  while 
possessing  many  better  qualities  for  chemical  ware  is,  when  well 
made,  scarcely  less  remarkable  for  beauty  than  crystal  lead  glass. 
Care  must  be  taken  in  the  selection  of  glass  apparatus,  espe- 
cially those  which  are  to  serve  as  implements  for  reactions,  to 
choose  such  as  are  free  as  possible  from  striae,  knots,  or  bubbles, 
— defects  owing  to  the  imperfect  mixture  of  the  materials  of  the 
glass.  They  should  have  great  uniformity  throughout  both  as  to 
material  and  workmanship.  The  more  transparent  the  glass,  the 
more  readily  can  the  interior  cleanliness  of  the  vessel  be  ascer- 
tained. The  common  green  glass  bottle  from  the  factories  of 
New  Jersey,  in  the  absence  of  better,  answers  every  purpose  for 
the  common  acids,  coarser  dry  substances,  and  the  solutions  of 
such  as  are  soluble ;  and  are,  moreover,  economical.  For  the 
reagents  and  finer  chemicals,  there  is  a  cheap  kind  of  white 
glass,  free  from  lead,  now  manufactured  in  Philadelphia,  and 
which  is  well  adapted  to  the  purposes,  and  satisfactorily  replaces 
the  elegant,  but,  at  the  same  time,  much  more  costly  imported 
Bohemian  glass.  The  laboratory  series  should  vary  in  size  from 
one  ounce  to  one  gallon,  ranging  as  follows :  1,  2,  4,  8,  16,  32, 
64,  128  ounces.  The  most  approved  shapes  are  shown  by  the 
cuts  below.  Fig.  49  represents  a  wide-mouth  bottle  for  powders 

and  crystals.      It   is  short 


Fig.  49. 


Fig.  50.          Fig.  51. 


and  wide,  with  round  shoul- 
ders to  admit  of  ready  empty- 
ing and  cleansing,  and  has  a 
strong  tall  neck  for  tightly 
corking.  The  corks  should 
be  perfectly  smooth  and  of 
the  velvet  kind.  This  shape 
is  equally  applicable  to  the 
bottles  of  white  glass,  as  is 
also  that  of  the  narrow  mouth, 
glass  stoppered,  as  shown  by 

Fig.  51.  The  narrow  necks  and  their  stopples  must  be  accu- 
rately ground,  so  as  to  insure  perfect  tightness.  As  the  cost  of 
this  white  glass  above  mentioned  is  so  very  little  greater  than  the 
Jersey  green,  it  would  probably  be  more  advisable  to  purchase 


THE  LABORATORY — THE   BOTTLES.  75 

the  whole  suite  of  bottles  of  such  material.  The  stopples  of  the 
narrow-necked  bottles  are  made  nearly  spherical,  but  somewhat 
flattened  on  the  top  to  project  over  the  mouth  so  as  to  protect  it 
from  dust.  The  lips  are  flat  and  stout  for  pouring  readily.  The 
wide-mouthed  stoppered  bottles  are,  as  to  body,  similar  in  shape 
to  the  above,  but  their  stopple-heads  are  flattened,  and  cover 
both  the  mouth  and  the  rim.  The  series  of  all  these  bottles  con- 
sists of  the  sizes  above  mentioned.  For  one  or  two  substances 
both  in  solid  state  and  solution,  which  are  sensitive  to  the  decom- 
posing influence  of  the  light,  nitrate  of  silver  and  protochloride 
of  mercury,  for  instance,  it  is  necessary  that  the  bottles  be  either 
of  dark-colored  glass,  or  else  covered  exteriorly  with  tin  foil. 
For  hydrofluoric  acid,  a  lead  or  gutta  percha  bottle  is  necessary, 
as  glass  is  decomposed  by  that  body.  All  solutions  should  be 
kept  in  ground-stoppered  bottles ;  and  if  economy  is  indispen- 
sable, let  the  series  consist  of  as  many  of  the  green  glass  bottles 
as  possible,  retaining  only  as  many  of  the  white  Bohemian  glass 
as  are  absolutely  necessary  for  the  finer  reagents.  Corked  bot- 
tles are  inconvenient  and  liable  to  leakage,  and  their  use  as  per- 
manent receptacles  of  liquid  should,  if  possible,  be  entirely  dis- 
carded. We  have  consequently  not  given  the  shape  of  a  narrow- 
mouthed  unstoppered  bottle,  though,  if  they  are  preferred,  the 
shape  of  Fig.  51,  without  the  stopper,  must  be  the  pattern. 

All  bottles  with  contents  must  be  labelled  in  full  and  with  sym- 
bols. This  injunction  as  to  labelling  applies  with  equal  force  to 
the  beaker  glass  upon  the  sand-bath  and  the  capsule  over  the 
lamp,  and  to  every  vessel  resting  upon  the  shelves  or  employed 
in  operations,  which  contain  any  substance  or  solid,  whether  the 
material  or  product  of  any  process.  An  omission  of  this  pre- 
caution frequently  leads  to  much  confusion,  and  occasionally  to 
serious  errors.  Thin  writing  paper  glazed  upon  one  side  with  a 
solution  of  gum  tragacanth,  and  divided  into  small  squares  of 
different  dimensions  to  suit  the  several  sizes  of  vessels,  answers 
very  well  for  the  purpose  of  labelling  operating  vessels;  but  the 
blue-bordered  labels  of  the  shops  are  much  more  convenient,  and 
fully  as  cheap ;  their  cost  being  12  cents  per  box  containing  from 
100  to  500  labels,  according  to  the  size  of  the  latter.  With  a 
pencil,  or  more  properly  pen  and  ink,  the  designation  may  be 


76 


THE    LABORATORY — THE    BOTTLES. 


Fig.  52 


written  on  the  label,  and  thus  completed,  it  is  to  be  pasted  on  the 
bottle.  For  bottles  containing  the  chemicals,  materials,  &c., 
these  paper  squares  are  equally  applicable,  but  for  the  test  series, 
upon  which  the  labels  are  to  be  permanent,  it  is  better  that  the 
names  be  etched  upon  the  glass  by  the  action  of  fluohydric  acid. 
Indelible  labels  may  also  be  made  extemporaneously,  according 
to  Schubert's  suggestion,  by  writing  the  letters  on  paper  with 
a  solution  of  one  part  of  oil  of  vitriol  in  six  parts  of  water,  dry- 
ing, and  then  exposing  it  to  a  moderate  heat.  The  written  letters 
being  thus  partially  carbonized,  form  an  indestructible  label. 

For  writing  on  glass,  Brunnquell  proposes  the  use  of  a  crayon 
formed  by  melting  together  4  parts  of  spermaceti,  3  parts  of 
tallow,  and  2  parts  of  wax,  and  when  the  whole  is  fluid,  stirring 
in  6  parts  of  red  lead  and  1  part  of  potash. 

Bottles  are  now  made  with  indelible  names  in  black  enamel, 
upon  a  white  ground ;  and  where  economy  is  an  object,  the  annexed 

label  (Fig.  52),  published  by 
Bullock  &  Crenshaw,  Phila- 
delphia, from  our  design,  will 
be  found  an  excellent  substi- 
tute. It  expresses  the  full 
name  of  the  article,  with  its 
symbol ;  and,  having  a  carbon 
ground,  will,  when  varnished  with  a  benzole  solution  of  caout- 
chouc, present  an  indestructible  surface. 

Let  it  be  a  cardinal  rule  of  the  laboratory,  that  no  experiment 
or  operation  shall  be  abandoned  even  for  a  moment  without  hav- 
ing the  containing  vessels  labelled.  Those  bottles  of 
the  test  series  which  are  receptacles  for  acids  or  other 
corrosive  liquids,  wholly  or  in  part  volatile,  should  be 
provided  with  ground  glass  caps.  Fig.  53  represents 
a  bottle  of  this  pattern  with  the  label  corroded  in  by 
fluohydric  acid.  The  mouths  of  all  the  test-bottles  should 
have  a  flange  in  order  to  facilitate  pouring.  The  last 
drop  of  liquid  generally  adhering  to  the  lip  can  be 
arrested  by  touching  it  with  the  stopple,  which  catches  and 
reconveys  it  to  the  bottle,  when  returned  to  the  mouth.  As 
there  is  such  frequent  annoyance  from  the  obstinate  adhesion  of 


Chloride  Calcium 
CaCl 


THE   LABORATORY — CLEANSING   OF   GLASSWARE. 


77 


the  stopper  in  the  bottle  containing  liquor  potassce,  it  would  be 
advisable  to  have  one  of  the  test-bottles  constructed  specially  for 
holding  that  substance.  The  stopper  should  then  be  dispensed 
with,  and  the  neck  of  the  bottle  made  straight,  so  that  when 
ground  on  the  exterior  to  fit  a  cap  like  that  in  Fig.  53,  the  joint 
may  be  tight.  A  little  care  in  preventing  any  dripping  down 
the  side  when  pouring  from  the  bottle  will  always  insure  an  easy 
removal  of  the  cap,  as  may  be  necessary. 

There  are  other  laboratory  uses,  independent  of  the  aforemen- 
tioned, to  which  bottles  are  applicable.  The  wide-mouthed,  when 
accurately  stoppered  and  rendered  air-tight  in  the  mouth  with  a 
little  lard  or  suet,  are  excellent  substitutes  for  jars,  for  the  re- 
ception and  safe  keeping  of  gases  which  are  soluble  in  water 
or  corrosive  of  mercury,  and  consequently  cannot  be  collected 
over  either. 

Cleansing  of  Crlassware. — When  bottles  or  glassware  are  greasy, 
the  aid  of  alkali  or  ashes  is  necessary  for  the  removal  of  the  dirt. 
In  open  vessels  bran  or  sawdust,  by  their  mechanical  action,  will 
cleanse  the  surface  of  grease.  In  either  case  hot  water  is  a  great 
assistant;  and  when  the  laboratory 
is  not  provided  with  a  jack  or  gene- 
rator, an  iron  or  copper  kettle,  Fig. 
54,  fitted  to  the  top  of  a  stove  or 
one  of  the  openings  in  the  top  of  the 
furnace,  is  a  convenient  vessel  for 
furnishing  a  constant  supply.  The 
rinsing  afterwards  may  be  with  cold 
water.  A  short  twine  brush,  similar 
to  that  used  by  housewives  for  wash- 
ing tea  things,  is  an  excellent  assistant  in  cleansing  operations, 
and  there  should  be  several  of  them  about  the  laboratory.  For 
alkali,  lime  as  an  example,  which  coats  the  sides,  a  little  common 
muriatic  acid  is  requisite.  When  the  dirty  matter  is  fixed  and 
resists  the  purifying  action  of  these  two  agents,  and  also  of  hot 
water,  resort  must  be  had  to  the  use  of  small  round  pebbles,  or 
very  coarse  sand,  which,  when  agitated  with  a  little  water  in  the 
interior  of  the  bottle,  gradually  removes  the  adherent  dirt,  and 
can  then  be  rinsed  out  with  clean  water.  Shot,  though  much  used, 
are  objectionable,  as  portions  of  the  metal  are  apt  to  be  left  upon 


Fig.  54. 


78  THE   LABORATORY — CLEANSING   OF   GLASSWARE. 

the  sides  of  the  bottle,  by  abrasion  of  their  surfaces.  Careless- 
ness in  leaving  behind  one  or  more  shot,  which  frequently  secrete 
themselves  in  the  crease  at  the  bottom,  may  result  in  injury  to 
the  next  contents  of  the  bottle,  if  it  be  solvent  of  metal.  The 
daily  ablution  of  apparatus  had  better  be  performed  at  the  close, 
and  after  the  labors  of  the  day,  so  that  the  advantage  of  the 
night  may  be  obtained  for  draining  and  drying.  Retorts  and 
beaked  vessels  should  be  ranged  on  shelves  with  circular  holes 
for  the  reception  of  their  beaks.  In  this  case  as  well  also  in 
that  of  open  vessels,  the  mouths  should  always  be  placed  down- 
wards. When  it  is]  necessary  to  dry  the  cleansed  vessel  for  im- 
mediate use,  it  may  be  well  wiped  with  a  towel  exteriorly  and 
then  placed  upon  a  moderately  heated  sand-bath,  which  will  soon 
expel  all  internal  moisture.  Wide-mouthed  vessels  can  be  dried 
with  a  cloth.  For  cleansing  test-tubes,  a  goose-feather  or  stick 
with  a  small  sponge  fastened  to  its  lower  end  is  very  convenient ; 
or,  still  better,  a  screw-ramrod. 

The  removal  of  corks  from  the  interior  of  bottles  is  effected 
by  an  instrument  consisting  of  four  strands  of  iron  wire,  of 
about  one  foot  length  each,  united  together  at  one  end,  and  at 
the  other  four  extremities  bent  into  an  angular  shape.  Being 
elastic,  there  is  no  impediment  to  its  passage  through  the  mouth 
of  the  bottle,  in  the  interior  of  which  it  is  made,  by  a  dexterous 
management,  to  catch  and  secure  the  cork,  which  can  then  be 
drawn  out  with  the  wire.  This  simple  little  instrument  is  to  be 
purchased  at  any  house-furnishing  bazaar.  A  very  convenient 
substitute  is  a  doubled  string ;  the  loop  thus  formed,  when  in- 
troduced into  the  bottle,  secures  the  cork  and  allows  its  easy  ex- 
traction. 

It  not  unfrequently  happens  with  ground-stoppered  bottles, 
in  cases  where  certain  substances  form  their  contents,  that  the 
stopple  adheres  so  firmly  as  to  resist  all  efforts  to  remove  it  with 
the  fingers.  It  is  then  necessary  to  tap  it  gently  and  alternately 
on  each  side  with  the  handle  of  a  spatula, — the  spatula  being 
held  by  the  blade,  and  the  bottle,  by  the  top  of  its  stopple,  while 
the  body  rests  on  the  table.  In  ordinary  cases  this  process 
loosens  the  stopper,  but  if  it  fails,  it  then  becomes  necessary 
to  carefully  expand  the  neck  over  the  flame  of  the  small  spirit- 
lamp,  and  in  order  that  it  may  be  uniform,  the  bottle  must 


THE   LABORATORY — THE    TEST-CASE.  79 

be  kept  constantly  revolving  in  a 'horizontal  position.  When 
sufficient  warmth  has  been  applied,  a  gentle  tapping  of  the 
stopple,  as  above  directed,  effects  its  removal.  After  the  neck 
of  the  bottle  has  cooled,  it  and  the  stopper  must  be  washed  and 
dried  before  the  latter  is  returned  to  its  place,  otherwise  it  will 
soon  become  tightened  again.  The  plan  sometimes  adopted  of 
inserting  the  head  of  the  stopper  in  a  chink  and  then  wrenching 
it  out  as  it  were  by  turning  the  bottle  with  the  hand,  is  not  ad- 
visable, as  it  endangers  the  safety  of  both  the  vessel  and  hand. 

When  the  lamp  is  used,  the  motions  must  be  dexterous  and 
careful,  so  as  to  confine  the  heat  to  the  neck  of  the  bottle,  for 
if  it  is  allowed  to  reach  the  stopper  also,  the  expansion  of  both 
being  then  equal,  the  removal  of  the  former  cannot  be  effected. 
The  success  of  the  effort  depends  upon  a  difference  of  tempera- 
ture between  the  stopple  and  the  neck  which  encloses  it.  Fric- 
tion, induced  by  drawing  a  string  constantly,  and  for  a  length  of 
time,  to  and  fro  around  the  neck  of  the  bottle,  is  sometimes  sub- 
stituted for  the  heat  of  a  lamp. 

When  the  cementing  matter  is  a  crystallized  salt,  hot  water 
placed  around  the  edges  will  loosen  the  stopper  by  dissolving  the 
salt ; — when  it  is  metallic  matter,  hydrochloric  acid  is  necessary, 
care  being  requisite  that  it  does  not  injure  the  contents  of  the 
bottle.  In  some  cases  olive  oil,  similarly  applied,  is  more  effec- 
tual than  either  hot  water  or  acid  ;  and  for  resins,  alcohol  is  most 
suitable. 

These  remarks  are  equally  applicable  to  nearly  all  kinds  of 
closed  glass  vessels.  Broken  glass  and  odd  stoppers  being  often 
needed  for  various  uses,  should  be  preserved  in  a  box  for  the  pur- 
pose. 

The  Test-case. — The  bottles  of  the  test-case  should  be  of 
white  glass,  entirely  free  from  lead,  and  accurately  fitted  with 
ground  stoppers.  As  they  are  constantly  in  use,  it  is  preferable 
to  etch  their  labels  upon  the  glass.  This  is  readily  done  by  the 
operator  himself,  who  has  only  to  coat  a  limited  space  of  the 
bottle  (see  Fig.  53)  with  melted  wax,  and  after  tracing  thereon, 
with  an  iron  style,  the  name  and  symbol  of  the  reagent  to  be 
contained  therein,  to  wet  the  marks  with  sulphuric  acid,  and 
then  sprinkle  on  some  finely-powdered  fluoride  of  calcium  (fluor 
spar).  The  fluohydric  acid  thus  set  free  attacks  the  glass, 


80          THE  LABORATORY — THE  TEST  SERIES. 

and  rendering  the  latter  opaque,  makes  the  lc  tters  appear  distinct, 
whilst  the  wax  protects  the  other  portion  from  its  action,  and  when 
removed,  presents  the  smooth  surface  of  the  glass.  Care  should 
be  taken  to  avoid  inhaling  any  of  the  escaping  vapor,  as  it  is 
highly  dangerous  in  its  effects  upon  the  sysetm. 

When  paper  labels  are  used  they  must  be  payed  over  with  a 
thick  coating  of  insoluble  varnish,  and  written  upon  with  incor- 
rodible ink.  The  former  consists  of  white  of  egg  (strained), 
which  is  to  be  applied  with  a  camel's  hair  pencil,  and  immediately 
coagulated  by  steam  heat  and  then  dried  in  an  oven  at  about 
212°  F. :  or  it  may  be  a  solution  of  caoutchouc  in  benzole.  The 
ink  is  made  by  dissolving  one  part  of  genuine  asphaltum  in  four 
parts  of  oil  of  turpentine,  and  adding  lampblack  to  render  it 
properly  consistent.  The  neatest  method  of  marking  the  labels 
with  the  ink  is  by  means  of  a  small  stamp  and  types.  When  the 
ink  has  dried,  the  varnish  is  to  be  applied  as  above,  but  prefer- 
ably after  the  label  has  been  pasted  (with  gum  tragacanth)  upon 
the  bottle.  The  transparent  film,  hardened  and  rendered  inso- 
luble by  heat,  presents  a  firm  resistance  to  strong  acids,  alkaline 
solutions,  and  other  reagents  ;  and,  moreover,  this  kind  of  label  is 
economical. 

The  test  series  should  consist  of  ninety-one  bottles,  all  of 
which  are  to  be  kept  on  the  shelf-stand  placed  on  the  top  of  the 
table  in  the  rear  and  resting  against  the  wall,  as  shown  at  Fig. 
38.  The  first  ten  bottles  should  be  narrow-mouthed  and  of  eight 
ounces  capacity,  to  contain  the  following  liquids  : 

1.  Sulphuric  acid  (pure),    .  .     ,         ?  .  S03. 

2.  "  "     (common),    .         *  \  ','  ***** '  *''  S03. 

3.  Hydrochloric  acid  (pure),  .  .  .  HCl. 

4.  "  "      (common),         '*;,-'      j.v  HCl. 

5.  Nitric  acid  (pure),         J^;        .         :    *  ;'.    «•..-;  N05. 

6.  "        "      (common),      ,    ..      ^r'"*' •<     ->•••-  NO5. 

7.  Aqua  ainmonise,  %    r         .*'•  .  .  NH^O. 

8.  Hydrate  of  potassa,  in  solution,  .  .  KO. 

9.  Carbonate. of  soda,          ,           *V         Mi  .*      :..'  i         NaO,C02. 
10.           "              ammonia,     ;   ,v  Jk.yji"','--*  :•.  NH40,C02. 

The  next  division  of  the  series  should  comprise  twelve  narrow- 
mouth  bottles,  of  six  ounces  capacity,  and  containing  liquids,  as 
follows : 


THE  LABORATORY — THE  TEST  SERIES.          81 

11.  Acetate  of  lead  (neutral),      f^f.    •  :>^*-;.      :-V\j  .      PbO,A~. 

12.  Chlorine  water,       .  .  -*-'j         .  .  Cl. 

13.  Absolute  alcohol,     « ,(  .,,         ,  '       *'.'  "     " .    *  .      C4H602. 

14.  Ether,        .  ._         ..       •     .         •-."•'*'   ^.. .;          •  C4H50. 

15.  Chloroform,     ^     .„    *>        .  .•*  '       • ,.'       ~'- .  .      C2HC13. 

16.  Chloride  of  ammonium,       .        W .  ••.-<'"        .  NH4Cl. 

17.  Oxalate  of  ammonia,     .  .    -  .  .      NH4O.O. 

18.  Phosphate  of  soda,.  .  ....  .  2NaO,PO5,HO. 

19.  Chloride  of  barium,      .  .  .  .      BaCl. 

20.  Sesquichloride  of  iron,       -.  f,  .-r  .'         .  Fe2Cl3. 

21.  Sulphate  of  magnesia,  .  .,  .  .      MgO,SO3. 

22.  Succinate  of  ammonia,       .  -.     .         .  .          '   NH4O,S 

The  third  division  should  consist  of  sixteen  four- ounce,  narrow- 
mouth  bottles,  containing  the  following  solutions : 

23.;  Sulphate  of  lime,    '      .        ' '.    t   "    .'' "    '. '  „'   .  .      CaO,SO?. 

24.  Sulphite  of  soda,    .  .        .    .  .'  V"         NaO,S02. 

25.  Acetic  acid,      .          -..^       ..          "..         ' £.?<•  .      A(=C4H3O3). 

26.  Oxalic  acid,  ..  '      '•  ^   '    /..,  ,        .  .:  O(=C2H3,HO). 

27.  Sulphide  of  ammonium,        .^.          ..          -  •   'J  •      NH4S-|-HS. 

28.  Acetate  of  soda,    ..         .';»          .yV      '   .  "i  Na6,A. 

29.  Nitrate  of  baryta,       .;.          v*  .. .-+          •,.    .  "„  ..     BaO,N05. 

30.  Baryta  water,     -   ..  ;.    "       ..*.       '  ..  .,:    ..<:,'  '     BaO+HO. 

31.  Chromate  of  potassa,    .  .  ;,  ,  „•     t-:-.;  .      KaO,  Cr03. 

32.  Sulphate  of  potassa,  >"  .    '        ..   '     \    .  KO,S03. 

33.  Chloride  of  calcium,     .          ";        ''J-  ,  ^  .      CaCl. 

34.  Bicarbonate  of  potassa,       .         '*..    '       •.  %  *          KO,2C02. 

35.  Nitrate  of  silver,         .^'     '    .  ^          ^  .•     AgO,NO5. 

36.  Sulphate  of  copper,  .  .  •  jv      .»•",'••  CuO,S03. 

37.  Protochloride  of  tin,      .  ...         ^,  ..  .      Sn,Cl. 

38.  Sulphide  of  sodium,       •    ..        '  •. .     '       '.  ^        ."  NaS,HS. 

The  fourth  division  should  consist  of  twelve  narrow-mouth 
bottles  of  two  ounces  capacity,  and  containing  liquids,  as  fol- 
lows : 

39.«Tartaricacid,     .  -.'  ..      ^  .'  '         .  .      T(=C8H4010). 

40.  Hypermanganate  of  soda,    .  '  .  .  .  — 

41.  Sulphate  of  alumina,     .          .  /         '  :."       ^Y  .      A12O3,3SO3. 

42.  Tincture  of  galls,     .  .  .  ...  — 

43.  Bi-tartrate  of  potassa,      .  .  ,r  .  .      KOyZT-fcHO.  • 

44.  Protonitrate  of  mercury,       .  .  •..         .  .  HgO,N05. 

45.  BicMoride  of  mercury,  .  <•       %   *^;%         .  .      HgCl2. 

46.  Ferrocyanide  of  potassium,  .  .  '  ! '  .  2K,Cfy. 

47.  Solution  of  indigo,  .-  .  ;  •       •''•*/•"  .  ' 

48.  Molybdate  of  ammonia,       .  .  •  .  .  ? 

49.  Sulpho-cyanide  of  potassium,     .  .          -Vi  "•  .      K,CyS.,. 

50.  Carbazotic  acid,        .  p~ 


82  fc:..      THE  LABORATORY  —  THE   TEST   SERIES. 

The  fifth  division  embraces  ten  reagents,  contained  in  one- 
ounce,  narrow-mouth  bottles  : 

51.  Hydro-fluosilicic  acid,  .';;          ....  Si,Fl2,HFl. 

52.  Nitrate  of  nickel,      .        -  ,.'      '^':   •    ,.  .  NiO,NO5. 

53.  Protonitrate  of  cobalt,     .....  CoO,NO5. 

54.  Arseniate  of  ammonia,         .  .  .        *•%••*  3NH40,As05. 

55.  Sodio-protochloride  of  palladium,  ...  — 

56.  Bichloride  of  platinum,          .  .  .  .  PtCl2. 

57.  Tefchlorideofgold,        .  .  .  .-          .  AuCls. 

58.  Hydrate  of  soda,       .  .  .  .  ,,         .  NaO. 

59.  Antimoniate  of  potassa,  .  .  .  .  KO,SbQ5. 

60.  Cyanide  of  mercury,  .  .  .•  .    .  HgCy. 

The  sixth  and  succeeding  divisions  comprise  solid  matters  which 
require  wide-mouth  bottles.  The  first  ten  bottles  should  be  of 
four-ounce  capacity. 

61.  Carbonate  of  lime,    .  .  .  .'          -.,-'  CaO,C02. 

62.  "    ,  baryta,       .  .  .  "         .  BaO,CO2. 

63.  Sulphate  of  lead,       .             ."'••>.'     >!*V;^  'V-    PbO,SO3. 

64.  Sulphuret  of  iron,  .             .            ".             .-  FeS. 

65.  Bisulphate  of  potassa,            .             .             .  •*••'*•'•  KO,2S03. 

66.  Dry  carbonate  of  soda,  ....  NaO,C02. 

67.  Mixed  carbonate  of  soda  and  potassa  (dry),  .      NaO,CO2-4-KO,C02. 

68.  Pulverized  charcoal,  ....  C. 

69.  Granulated  zinc,        .  .           .             .             .  .      Zn. 

70.  Nitrate  of  potassa,  .            .            .            .  -  KO,N05. 

The  seventh  division  should  comprise  nine  two-ounce  bottles. 


71.  Fluoride  of  barium,           .             .  .',   rr    .\          • 

72.  Chlorate  of  potassa,     .             .  .   /*                       KO,Cl05. 

73.  Copper  wire  clippings,      .             .  "     .             .         ^^.l,    Cu... 

74.  Iron  wire  clippings,   .         .  '  ,%  .             .                          Fe. 

75.  Cyanide  of  potassium,    s-m            .  .             .             .      KCy. 

76.  Dry  carbonate  of  potassa,       ....  KO,COa. 

77.  Starch  paste,         .              .             .  .             .                      — 

78.  Hydrated  teroxide  of  bismuth,  .             .             .             Bi03,HO. 

79.  Oxide  of  lead,      .„.         -  .             .  "  >            .             .      PbO. 

The  eighth  division  should  consist  of  twelve  one-ounce  bottles. 

80.  Iodide  of  potassium,              .  .          :s,      KI. 

81.  Ferri-cyanide  of  potassium,          .  .             3K,2Cfy. 

82.  Biborate  of  soda,        .             .  .'          .       NaO,2B03. 

83.  Oxide  of  barium,              .            .  v   *             BaO,HO. 

84.  Nitro-prusside  of  sodium,      ".  «             .      Fe2Cy5,N02,Na2  +  4HO. 

85.  Peroxide  of  mercury,      .             „  .             HgO2. 

86.  Phosphate  of  soda  and  ammonia,  .            .      HO,NH40,NaOP05+8HO. 


THE  LABORATORY — THE  TEST  SERIES.          83 

87.  Blue  litmus  paper,      ,-•        *.'*<£*  ••*»,->     :--M*r*'  — 

88.  Red      "        «        ;  .;  r      ^  ,.,-     -,        ,,  ,    ,  — 

89.  Turmeric       "  J,   ^        '.          "V  '      'V'  ,   ? 

90.  Georgina        "  .    '         .        •    .     •;.."  .' ;  — * 

91.  Lead  « 

A  leaden  or  gutta-percha  bottle,  with  a  closely  fitting  stopper, 
and  of  two  ounces  capacity,  for  the  fluohydric  (HF)  acid,  com- 
pletes the  series. 

All  these  bottles  should  be  made  heavy,  for  if  too  thin,  being 
so  frequently  handled,  they  are  liable  t&  be  broken.  Of  the 
preceding  numbers,  1,  2,  3,  4,  5,  6, .  7,  8,  14,  27,  should  be 
furnished  with  ground  glass  caps,  as  shown  by  Fig.  53.  No. 
35  must  be  of  dark  glass,  or  else  covered  exteriorly  with  black 
paper.  Nos.  87,  88,  89,  90,  91,  should  always  be  accompanied 
with  a  pair  of  pincers  with  platinum  points,  similar  to  those 
used  in  blowpipe  operations,  as  the  test  papers  should  never 
be  handled  with  the  fingers.  The  bottles  for  alcohol  (C4H602) 
and  distilled  water  (HO)  may  be  of  common  green  glass,  narrow- 
mouthed,  and  quart-size.  They  are  fitted  with  double  tubes  so 
as  to  admit  the  air  gradually,  and  thus  promote  a  gentle  flow  of 
the  liquid  from  them,  in  the  act  of  pouring ;  and  are  designed  as 
conveniences  to  the  operating-table,  for  supplying  small  quanti- 
ties of  their  contents  to  test  tubes  and  narrow-mouthed  vessels 
without  the  aid  of  a  funnel.  Fig.  55  shows  their  form  and  ar- 
rangement. 

A  piece  of  bright  copper,  and  one  of  iron,  are  also  frequently 
needed  as  reagents. 

All  of  the  forenamed  reagents  must  be  chemically 
pure,  as  also  the  water  used  in  making  solutions  of 
them. 

The  reservoir  for  distilled  water  should  be  a 
close  jar  of  blue  stoneware  or  white  iron  stone 
china,  the  glazing  of  which  is  free  from  lead ;  and 
it  must  have  a  glass  cock  near  the  bottom  through 
which  to  draw  off  supplies  for  use,  as  may  be  re- 
quired. 

Besides  the  reagents,   a   small   stock   of  which 
should  always  be  kept  in  reserve  on  the  shelves  of  the  cupboard, 
there  is  required  a  general  assortment  of  drugs  and  chemicals  in 


84  THE   LABORATORY. 

limited  quantity.  The  coarser  and  cheaper  articles  of  this  stock 
should  preferably  be  purchased  from  the  dealers,  but  it  is  advi- 
sable for  the  operator  to  prepare  the  costlier  ones  for  himself, 
not  only  on  the  score  of  economy,  but  also  because  of  the  prac- 
tice which  he  will  acquire  in  the  manipulations  of  various  pro- 
cesses. 

There  remain  but  few  points  to  be  remarked  upon  before 
closing  our  chapters  upon  the  laboratory.  We  have  already  en- 
joined upon  the  experimenter  great  cleanliness,  and  we  now  re- 
peat the  injunction.  The  hands  should  always  be  free  from  dirt, 
and  invariably  washed  with  castile  or  palm  soap  before  going  to 
meals.  This  precaution  is  absolutely  necessary  on  account  of 
health,  for  otherwise,  in  working  with  deleterious  matters,  the 
minute  particles  which  secrete  themselves  under  and  around  the 
finger  nails,  may  be  conveyed  into  the  system,  and  thereto  work 
an  injury.  So,  also,  when  engaged  at  one  time  upon  several 
operations  of  a  different  nature,  it  is  necessary  to  rinse  the  hands 
in  passing  from  the  management  of  one  to  that  of  another  of 
them.  For  this  purpose,  the  hydrant  or  reservoir  with  its  ad- 
joining hand-towel,  Fig.  30,  ia  very  convenient. 

To  protect  the  person  from  dirt,  the  operator  should  provide 
himself  with  a  suitable  costume.  A  long  wrapper  of  linsey  or 
baize  for  winter,  and  of  Holland  linen  for  summer,  is  very  suit- 
able. A  light  cap  of  some  cheap  material,  is  a  good  shield  to 
the  hair  against  the  bad  effects  of  dust  and  vapor. 

In  all  investigations,  the  practice  of  working  upon  small  quan- 
tities will  lead  to  habits  of  nice  and  delicate  manipulation.  Be- 
sides, it  is  easier,  less  costly  and  fatiguing  to  manage  a  small 
portion  of  any  substance. 

There  are  three  blank  books  requisite  in  every  laboratory. 
The  first  may  be  called  the  Laboratory  Record,  as  it  is  de- 
signed to  contain  full  notes  of  the  progress  of  every  experiment 
and  operation  going  on  in  the  laboratory.  In  this  way,  a  large 
store  of  valuable  facts  is  preserved  for  future  reference.  The 
second  book  is  the  Record  of  Analyses,  in  which  are  transcribed 
the  results  of  analyses  of  such  substances  as  may  have  undergone 
examination  in  the  laboratory.  The  mode  of  analysis  may  also 
be  included.  This  record  is  also  very  useful  for  future  reference. 
The  other  book  is  an  "Index  rerum,"  after  the  plan  of  the  Rev. 


INDEX  RERUM.  85 

J.  Todd,  author  of  the  Student's  Manual.  As  it  is  impossible 
to  retain  all  that  one  reads,  and  much  heing  valuable,  some  other 
means  more  practicable  and  less  laborious  than  copying  out  ex- 
tracts must  be  adopted  for  preserving  its  remembrance.  Mr.  Todd 
recommends  the  habit  of  making  an  index  rerum  in  reading. 
This  book  consists  of  several  quires  of  blank  sheets,  letter  form, 
and  is  alphabetically  classified,  so  as  to  exhibit  at  a  glance,  the 
name  of  the  book  and  the  number  of  the  page  treating  of  the 
subject,  the  synopsis  of  which  is  recorded  under  its  appropriate 
letter  and  heading.  Such  a  digest  of  journals  and  books,  though 
very  meagre,  will  still  present  their  notable  points,  and  prove  an 
all-sufficient  key,  when  making  researches  in  the  future  upon  any 
subject  about  which  it  is  desired  to  have  all  existing  information. 
Always,  as  Mr.  Todd  directs,  have  your  index  at  hand  when  read- 
ing book,  journal,  pamphlet,  or  newspaper ;  and  "  when  you  meet 
with  anything  of  interest,  note  it  down,  the  subject,  the  book,  the 
volume,  and  the  page ;  and  make  your  index  according  to  sub- 
jects as  much  as  possible,  selecting  that  word  for  the  margin 
which  conveys  the  best  idea  of  the  subject,"  so,  that  there  may 
be  no  difficulty  in  finding  the  original  place  when  it  is  necessary 
to  refer  to  it.  The  following  are  a  few  examples  of  the  manner 
in  which  the  digests  should  be  recorded : — 

A  1  New  theory  of  their  constitution,  by  James  C.  Booth, 

ACIDS  FATTY.     J        Journal  of  the  Franklin  Institute  for  1848. 

I  Investigation  of  the  properties  of,  by  M.  Payen,  Chem. 
GUTTA-PERCHA,  j  Gaz.  1852,  p.  176. 

I  New  mode  of  making,  with  Silica  and  Sodium,  by  St. 
SILICIUM.         j         Clair  Deville,  Comptes  Rendus,  1855,  p.  1053. 

There  are  many  other  minutiae  that  might  be  mentioned,  but 
for  want  of  room  for  more  important  matter ;  and  so  we  leave 
them  to  be  suggested  by  experience. 

Habits  of  industry,  close  observation,  and  neatness,  are  in- 
dispensable to  the  acquisition  of  skill  in  manipulating,  and  without 
them  it  will  be  difficult  to  become  an  accurate  chemist. 

The  laboratory  which  we  have  described,  is  well  appointed  for 
every  branch  of  research.  Many  of  the  implements  enumerated 


86  DIVISION   OF   SUBSTANCES. 

may  be  dispensed  with  for  ordinary  operations,  but  they  are 
requisite  for  a  complete  arrangement,  which,  as  given  in  the  pre- 
ceding chapters,  is  not  at  all  extravagant.  Moreover,  with  a 
little  extra  industry,  the  operator  can  soon  realize  the  outlay  for 
all  conveniences,  in  the  manufacture  and  sale  of  such  pure  chemi- 
cals as  may  be  in  demand.  We  have  provided  him  with  every 
appliance  for  the  purpose,  so  that  his  self-improvement  may  be 
attended  also  with  pecuniary  profit. 

Where  the  means  are  limited,  it  is  better  that  the  purchase  of 
apparatus  should  be  gradual,  commencing  with  those  pieces  which 
are  of  most  general  use.  This  course  judiciously  carried  out, 
will  in  time  secure  a  well-stored  laboratory.  All  stock  and  appa- 
ratus can  be  bought  from  the  manufacturer,  or  importer,  at  very 
little  over  one-half  the  dealer's  prices,  for  the  same  articles. 


CHAPTER  IV. 

DIVISION   OF   SUBSTANCES. 

THIS  operation  is  a  mechanical  process,  by  which  the  surface 
and  points  of  contact  of  solid  bodies  are  multiplied ;  thus  dimi- 
nishing, in  a  high  degree,  the  opposing  force  of  cohesion,  and, 
consequently,  by  promoting  greater  access  to  its  particles,  en- 
abling the  more  ready  and  rapid  action  of  reagents  upon  solid 
matter. 

The  means  by  which  the  division  of  solid  matters  is  accom- 
plished are  manifold,  and  vary  with  the  nature  of  the  substance 
to  be  reduced ;  some  bodies  being  pulverizable  by  almost  any  of 
the  processes,  while  others  again  require  a  particular  method  for 
their  reduction.  The  different  modes  of  operating  may  be  classi- 
fied as  follows : — 

1st.  Slicing. — This  process  applies  to  fibrous  matters,  and  is 
practised  with  a  spring  lever-knife,  similar  to  that  used  by  to- 
bacconists for  cutting  tobacco,  and  shown  by  Fig.  56. 

Being  thus  reduced  to  thin  slices,  the  substance  is  in  better 
form  for  maceration,  &c. ;  and,  moreover,  admits  of  readier  desic- 


CRUSHING. 


87 


cation,  a  necessary  process  when  it  is  required  to  be  further 
reduced  under  the  pestle,  or  by  being  grated  on  a  coarse  rasp. 

Fig.  56. 


This  mode  of  pulverization  by  rasping,  though  particularly 
applicable  to  fibrous  substances,  such  as  fresh  roots  and  the  like, 
is  sometimes  used  for  metals  and  hard  matters.  In  the  latter 
case,  the  files  must  have  finer  and  sharper  teeth,  and  in  both 
instances  be  perfectly  clean,  and  free  from  grease  and  dust. 

Fig.  57. 


2d.  OwsAw#. — Fresh  roots  and  juicy  vegetable  matters  of  a 
tough,  stalky,  and  fibrous  nature,  which  are  not  required  to  be 
reduced  under  the  knife,  may  be  better  prepared  for  the  action 
of  solvents  or  the  press,  by  being  crushed  under  the  pestle  in  a 
common  mortar.  As  this  mode,  however,  is  very  tedious,  and 
. 

.- 


88 


CRUSHING. 


inapplicable  even  to  moderately  large  quantities,  it  is  best  to  use 
a  machine  -which  has  been  devised  for  the  purpose  bj  Coffey. 
It  is  shown,  in  section  and  elevation,  by  Figs.  57,  58,  and  consists 
a  cast  iron  frame  F  F,  on  which  is  set  a  pair  of  hard  wooden 
rollers  revolving  towards  each  other,  and  fed  from  a  hopper  C 
with  the  material  to  be  crushed.  The  latter,  as  it  passes  through 

Fig.  58. 


the  rollers,  falls  into  a  receiver  D  beneath.  The  gearing  com- 
prises a  fly-wheel  G,  a  spur-wheel  H,  and  the  cog-wheels  1 1. 
Being  put  in  motion  by  turning  the  handle,  which,  however,  re- 
quires considerable  power,  the  rollers  draw  the  material  through, 
and  drop  it  in  the  reseiver  in  a  thorough  state  of  contusion.  It 
must  be  mentioned,  however,  that  some  tough  substances  require 
to  be  passed  through  the  rollers  several  times  before  they  become 
thoroughly  crushed;  and  for  such  cases,  the  wheels  B  B,  com- 
municating with  the  rollers,  serve  to  regulate  the  distance  between 
the  two,  as  may  be  necessary  for  widening  it  at  the  first  step, 
and  closing  at  the  final  operation.  In  this  way,  the  hard  as  well 
as  the  soft  parts  of  the  substance  become  uniformly  crushed;  and, 
the  crushed  matter  may  be  pressed,  without  passing  any  sus- 
pended particles  of  woody  fibre  with  the  juice. 


PULVERIZATION.  89 

3d.  Pulverization. — In  order  to  obtain  a  minute  division  of 
the  denser  substances,  whose  particles  are  very  cohesive,  resort 
must  be  had  to  the  pestle  and  mortar.  The  material  of  this  ap- 
paratus varies  with  the  nature  of  the  substance  to  be  powdered. 
To  prevent  errors,  corrosive  or  caustic  matter  should  never  be 
pulverized  in  metallic  mortars,  else  by  a  solution  of  a  portion,  or 
contamination  with  abraded  particles,  unavoidable  confusion  will 
ensue.  The  resistant  nature  of  the  material  of  the  mortar  must 
be  proportional  to  the  hardness  of  the  body  to  be  operated  upon. 
For  the  harder  insoluble  substances,  those  of  iron,  or  steel, 
are  generally  used.  For  the  less  dense  and  more  pulverizable 
bodies,  especially  those  which  are  acid,  or  corrosive,  porcelain, 
wedgwood,  or  glass,  is  the  proper  material.  Marble,  being 
readily  attacked  by  acids,  mortars  of  that  material  are  only  used 
for  reducing  those  inert  substances  which  are  readily  comminuted 
merely  by  trituration,  such  as  chalk,  neutral  salts,  &c.  This 
material,  as  well  as  glass,  is  well  replaced  by  porcelain  or  wedg- 
wood, which  are  stronger,  and  otherwise  much  less  objectionable. 
There  should  be  an  assorted  series  of  mortars  for  laboratory 
purposes. 

The  large  iron  mortar  has  its  position  in  the  furnace-room,  and 
is  permanently  and  firmly  fitted  upon  ,an  upright  block  of  hard 
wood,  Fig.  59,  in  some  convenient  place,  for  general  use,  in 
pounding  ores,  metals,  and  coarser  substances.  The  pestle  of 
this,  as  .of  all  other  mortars,  should  invariably  be  of  one  piece 
and  of  the  same  material  as  the  mortar ;  because,  when  the  lower 
part  is  fitted  to  a  handle,  it  is  apt  to  become  loosened  and  drop 
off  particles  of  the  cement  with  which  it  is  fastened,  to  the  injury 
of  the  contents  of  the  mortar.  The  handle  or  upper  portion  must 
afford  convenient  space  for  grasping,  and  the  base  or  lower  por- 
tion, roughened  on  its  face  by  use  of  sand,  should  diverge  to  a 
diameter  of  about  one-fourth  of  that  of  the  mouth  of  the  mortar. 
Fig.  60  exhibits  a  mortar  of  proper  form  and  proportionate  thick- 
ness as  to  its  different  parts.  Its  interior  form  is  nearly  that  of 
the  butt  end  of  an  egg,  so  as  to  promote  a  constant  contact  of  the 
matters  under  process,  with  the  rotating  pestle.  To  prevent  the 
ejection  of  particles  of  matter  or  the  escape  of  dust,  and  conse- 
quent inconvenience  to  the  operator,  as  the  case  may  be,  the 
mortar  should  be  provided  with  a  sheep-skin  conical  coverlet, 


90 


MORTARS. 


Fig.  59. 


with  a  hole  in  its  centre  for  the  passage  of  the  pestle,  which  is  to 

be  fastened  around  its  rim  and 
over  its  mouth,  with  a  string. 
Circular  pasteboard  and  wooden 
covers,  of  eizes  corresponding 
with  the  mortars  and  with  a 
hole  in  their  centres,  are  often 
substituted  for  the  conical  co- 
verlet. The  operator  should 
always  stand  with  his  back  to  a 
current  of  air;  and  to  further 
guard  against  the  unpleasant  or 
deleterious  effects  of  the  fine 
dusty  particles  which  may  arise 
from  the  mortar,  he  can  moisten 

Fig.  60. 


its  contents  with  a  little  water,  provided  that  liquid  is  without 
action  upon  the  substance.  Exposure  to  warmth,  for  the  evapo- 
ration of  the  water,  will  restore  the  matter  to  its  original  dryness. 

All  substances  formed  of  an  organic  tissue  should  be  previously 
dried,  so  as  to  afford  greater  facility  in  their  pulverization,  but 
care  must  be  observed  to  avoid  a  heat  sufficiently  high  to  injure 
their  properties.  A  previous  reduction  of  ores,  and  coarse  hard 
substances  into  lump,  by  concussion  with  a  hammer  upon  an 
anvil,  and  of  roots  and  the  like  into  slices  or  bits  with  a  common 
knife  or  lever-cutter  (Fig.  56),  are  preliminary  processes  which 
greatly  facilitate  their  pulverization.  The  substance  to  be  struck 
upon  the  anvil  should  be  previously  wrapped  in  strong  brown 
paper. 

Silicious  stones  pulverize  much  more  readily  after  having  been 


MORTARS. 


91 


heated  to  redness  in  a  crucible,  and  in  that  state  projected  into 
cold  water.  This  increased  friability  is  occasioned  by  the  unequal 
cooling  of  the  mass. 

Metals,  alloys,  and  the  like,  which  are  difficultly  pulverizable 
whilst  cold,  may  also  be  readily  crushed  when  heated  to  redness. 

When  it  is  required  to  reduce  the  substance  into  small  frag- 
ments only,  it  can  be  broken  down  by  a  succession  of  blows  with 
the  pestle.  If  the  substance  is  very  hard,  the  foroe  of  the  arm 
should  be  added  to  the  descending  weight  of  the  pestle,  so  as  to 
impart  power  to  the  blow.  A  subsequent  circular  grinding  mo- 
tion of  the  pestle,  continued  for  a  length  of  time,  will  further 
reduce  these  fragments  to  fine  powder,  and  consequently  this 
movement  must  be  avoided  when  only  a  coarse  comminution  is 
desired.  The  mortar  must  always  rest  upon  a  solid  foundation, 
and  during  the  operation  of  pounding  should  be  occasionally 
shaken,  in  order  that  the  coarser  particles  which  mount  to  the 
sides  may  be  forced  back  to  the  centre  of  the  mortar,  so  as  to 
receive  the  full  effects  of  the  descending  pestle,  which  should 
never  be  allowed  to  strike  the  sides  of  the  mortar.  If  the  sub- 
stance is  to  be  reduced  to  a  fine  powder,  the  process  is  greatly 
facilitated  by  operating  upon  only  a  small  portion  at  a  time,  as 
the  pestle  is  less  liable  to  become  clogged. 

In  the  analysis  of  rare  minerals,  especially  those  which  are 

Fig.  61. 


very  hard,  the  reduction  is  effected  in  a  small  mortar  of  hardened 
steel.  This  apparatus,  shown  by  Fig.  61,  consists  of  three  sepa- 
rable pieces,  each  of  which  is  smoothly  turned,  so  as  to  present 


92  TEITURATION. 

an  even  surface  exteriorly  and  interiorly.  C  is  the  base  piece, 
into  the  cavity  of  which  the  cylinder  B  fits  somewhat  loosely. 
It  is  this  cylinder  which  receives  the  mineral  to  be  reduced. 
Sliding  into  it  is  the  exactly  fitting  pestle  A,  which  being  struck 
successively  with  a  hammer,  crushes  the  mineral  to  powder  with- 
out waste  of  any  of  its  particles  by  ejection. 

When  the  powder  thus  obtained  is  not  yet  sufficiently  fine  for 
analysis,  it  must  be  transferred  to  an  agate  mortar,  and  rubbed 
with  the  pestle  until  reduced  to  an  impalpable  state.     The  pestle 
and  mortar  are  of  the  same  material,  the  hardness  and  smooth- 
ness of  which  render  it  particularly  applicable  for  the  purpose. 
The  motion  of  the  pestle  should  always  be  circular,  otherwise  a 
perpendicular  blow  may  endanger  the  safety  of  the  mortar,  espe- 
cially if  it  has  a  fissure,  as  is  often  the  case,  running  through  it. 
The  given  weight  of  the  mineral  for  analysis  must  always  be  esti- 
mated after  pulverization ; — never  previously,  lest  a  loss  by  ejec- 
tion, or  adhesion  to  the  mortar  or  spatula,  may  lead  to  inexact 
results.     Fig.  62  exhibits  an  agate  mortar,  which 
Fig.  62.         can  j^  purchased  of  sizes  varying  from   1  to  6 
inches  in  diameter.     One  of  about  3J  inches  width 
will  be  most  useful.     It  should  be  selected  as  free 
from  indentations,  fissures,  or  cavities  as  possible, 
for  these  faults  not  only  impair  the  durability  of 
the  mortar,  but  render  its  cleansing  very  difficult.     An  excellent 
plan  of  removing  tenaciously  adhering  matter  from  the  sides  or 
bottom  of  a  mortar,  is  to  rub  them  with  pumice-stone  and  water. 
4th.   Trituration. — This  mode  of  manipulating  with  the  pestle 
is  application  to  those  substances   which  are  friable,  and  fall  to 
powder  by  being  merely  rubbed  up  by  a  circular  or  grinding 
motion  of  the  pestle,  and  which  would  soften  and  become  obsti- 
nate by  being  pounded.     Chalk  and  the  like,  and  most  of  the 
salts,  are  in  the  first  category  ; — the  resins  and  gum-resins  in  the 
second. 

Sand  is  added  to  facilitate  the  reduction  of  resins  and  similar 
substances,  which  cake  under  the  pestle,  only  when  they  are  in- 
tended for  maceration  or  solution.  Under  other  circumstances, 
the  medium  would  be  an  adulterant  on  account  of  the  impossibility 
of  separating  it. 

The  proper  material  for  a  mortar  for  this  purpose  is  white 


TRITURATION.  93 

wedgwood,  of  form  as  shown  by  Fig.  63.  Berlin  porcelain 
mortars,  glazed  outside  and  biscuit  internally,  with  broad-butted, 
solid  pestles,  as  shown  at  Fig.  64,  are  neat  and  convenient  im- 
plements, but  less  available  for  general  purposes  than  those  of 

Fig.  63.       •  Fig.  64. 


wedgwood,  which  are  stronger,  more  durable,  and  will  stand 
harder  blows.  These  are  purchased  by  the  diametrical  inch,  and 
the  most  convenient  size  is  6  to  8  inches  width  at  the  mouth.  It 
will  be  well  also  to  have  a  smaller  one  of  the  same  material,  say 
of  2  inches  diameter  at  the  top. 

Fig.  65. 


Hewitt  proposes  to  reduce  the  amount  of  labor  and  time  re- 
quired in  the  use  of  mortars,  by  the  substitution  of  machinery  ; 


94 


TRITURATION. 


and  to  this  end,  has  presented  an  ingenious  invention,  Fig.  65, 
which  imitates  exactly  the  rotating  motion  given  to  the  pestle  by 
the  hand.  The  weight  of  the  pestle  of  this  machine  is  12  to  14 
pounds,  and  its  gearing  and  action  are  intelligibly  expressed  by 
the  drawing. 

It  is  said  to  require  very  little  power,  and  that  only  from  the 
hand.  Aloes,  cantharides,  and  similar  substances,  are  reduced  to 
fine  powder,  by  its  means,  with  great  promptness;  moreover,  it 
moves  noiselessly,  and  does  not  scatter  dust. 

Another  machine,  of  similar  purport,  but  of  more  extended  ap- 
plication than  the  above,  both  as  regards  the  varieties  of  sub- 
stances and  the  quantities  which  may  be  operated  upon,  is  that 
known  as  Goodall's  grinding  and  levigating  apparatus,  shown  by 
Fig.  66.  In  this,  as  in  the  former  invention,  the  pestle  acts 

Fig.  66. 


from  a  motion  similar  to  that  imparted  by  the  hand ;  and  as  it 
traverses  a  different  surface  each  rotation,  no  scrapers  are  re- 
quired to  keep  the  powder  constantly  under  action.  Steam- 
power  increases  the  efficiency  of  the  apparatus;  but  it  acts 
readily  with  hand-power,  even  upon  the  hardest  substances. 


PORPHYRIZATION.  95 

A  weighted  lever  secures  the  pestle  at  the  top,  and  the  gearing 
from  which  it  derives  motion  is  driven  by  a  bevel-toothed  cog- 
wheel on  the  main  driving-shaft,  which  is  provided  with  a  winch- 
handle.  The  mortar  is  placed  in  front,  to  be  wholly  out  of  the 
way  of  falling  dust  and  dirt  from  the  moving  wheels  and  other 
parts  of  the  machinery. 

The  pestle  being  attached  to  the  driving-shaft  by  a  screw  can 
be  removed  as  may  be  required. 

5th.  Porphyrization. — This  mode  of  pulverizing,  only  em- 
ployed when  it  is  required  to  reduce  the  powder  to  the  greatest 
fineness,  takes  its  name  from  that  of  the  material  of  the  vessels 
in  which  it  is  practised.  A  small  porphyry  mortar,  hemispheri- 
cal interiorly,  or,  preferably,  a  slab  and  muller,  is  the  apparatus 
employed.  Flint,  and  even  glass,  which  are  equally  as  hard  as 
porphyry,  form  an  economical  substitute  for  that  material.  It  is 
highly  important  that  the  material  of  the  apparatus  shall  be  less 
easily  abraded  than  the  substance  being  ground ;  for  if  too  soft, 
the  latter  becomes  contaminated  with  the  particles  which  are 
rubbed  off,  and,  hence,  in  exact  investigations,  inaccuracy  is 
occasioned. 

Porphyrization  is  generally  effected  by  rubbing  the  coarse 
powder  between  a  flat  slab  and  muller,  until  reduced  to  an  im- 
palpable state.  The  circular  motion  of  the  muller  disperses  the 
powder  over  the  slab,  rendering  it  frequently  necessary  to  collect 
it  together  in  the  centre  with  a  spatula,  so  as  to  keep  it  uniformly 
under  the  action  of  the  muller.  The  spatula  may  be  of  horn  or 
steel,  but  is  better  when  of  platinum.  Fig.  67  exhibits  a  slab 
and  muller.  When  the  substance  under 
operation  is  unalterable  by  water,  it  may  ^ig'  67> 

be  moistened  with  that  liquid,  which,  by  C\ 

converting  it  into  a  paste,  facilitates  its       i_JI 

reduction,  and  prevents  any  waste  by  the     ^  "iii'!!;;i 

escape  of  dusty  particles.     The  powdered 

paste  is  easily  dried  by  being  dropped  in  dots  upon  a  porcelain 
plate  and  exposed  to  warmth.  Those  matters  which  are  soluble 
in  or  alterable  by  water,  must  be  porphyrized  in  a  dry  state. 

6th.  Sifting. — The  impossibility  of  reducing  the  whole  of  a 
substance  at  once  to  a  uniform  state  of  fineness  by  any  of  the 
preceding  processes,  renders  necessary  an  occasional  separation, 


96  SIFTING. 

during  the  progress  of  pulverization,  of  the  more  comminuted 
portions  from  the  grosser  particles.  This  is  effected  by  means 
of  a  sieve,  of  which  there  should  be  several  in  the  laboratory.  A 
wooden  cylinder  of  about  four  inches  depth,  with  an  accompany- 
ing ring  of  the  same  materials,  constitutes  the  frame,  over  which 
can  be  stretched  a  cloth  of  any  required  fineness.  For  coarser 
articles,  fine  brass  wire  is  the  best  material  for  the  cloth,  but 
when  the  powder  is  to  be  impalpable,  bolting  cloth  (raw  silk),  or 
gauze  is  requisite.  Sieves  are  also  covered  with  hair-cloth,  buck- 
ram, book-muslin,  and  iron  wire  of  different  sized  meshes,  each 
of  which  has  its  appropriate  application.  The  metallic  sieves 
should  have  their  cloths  permanently  fitted  to  them.  For  all  the 
rest,  two  frames,  as  above  described,  one  of  much  larger  dimen- 
sions than  the  other,  will  serve  ;  as  it  is  only  necessary  to  remove 
the  ring  when  it  is  desired  to  substitute  one  kind  of  covering  for 
another.  The  sieves  of  cloth,  of  graduated  fineness,  can  be  kept 
in  some  secure  place,  and  withdrawn  as  wanted,  and  thus  we 
have  the  economical  means  of  possessing  a  full  suite  of  sieves 
from  the  metallic  wire,  through  all  the  grades  of  fineness  up  to 
the  closest  wrought  bolting-cloth.  The  form  of  a  sieve  is  shown 
at  A,  Fig.  68.  After  the  separation  of  the  finer  portions  by  the 
sieve,  "the  coarser  particles  are  again  sub- 
Fig  68.  jected  to  grinding  and  sieving  as  often  as 
is  necessary  to  convert  the  whole  into  the 
requisite  state  of  uniform  fineness.  Horn- 
scoops,  or  porcelain  spoons,  or  ladles,  are 
the  proper  implements  for  transferring 
the  contents  of  the  mortar  to  the  sieve. 
In  some  cases,  a  stiff  pasteboard  card, 
being  more  pliable,  is  a  convenient  sub- 
stitute. The  use  of  the  hand,  for  this 

purpose,  should  always  be  avoided  as  a  slovenly  practice.  A 
platinum,  horn  or  bone,  or,  less  preferably,  steel  spatula  may,  be 
used  to  detach  the  particles  adherent  to  the  sides  of  the  mortar. 
To  prevent  inconvenience  or  injury  to  the  operator  (who,  both  in 
powdering  and  sieving,  should  always  stand  with  his  back  to  a 
current  of  air),  from  particles  of  dust  or  acrid  poisonous  matter, 
as  well  also  to  avoid  waste,  the  sieve  should  be  fitted  with  a  top 
and  bottom  covering,  as  shown  at  B  and  C,  in  Fig.  68,  the  upper 


SIEVES.  97 

of  which  arrests  the  escape  of  the  light  dust  into  the  air,  and  the 
lower  receives  that  portion  which  passes  through  the  cloth. 
These  covers  are  headed  with  parchment  or  calf-skin,  and  the 
three  divisions,  when  joined  together,  form  what  is  called  a  drum 
or  box-sieve.  The  powder  is  made  to  pass  through  the  meshes 
by  gently  agitating  the  sieve  between  the  hands.  A  rough  jar- 
ring motion  will  force  through  some  of  the  coarser  particles,  and 
thus  destroy  the  uniformity  of  the  powder ;  and  hence  the  com- 
mon practice  of  tapping  it  frequently  against  the  side  of  the 
mortar  should  be  abandoned,  unless  the  state  of  fineness  is  imma- 
terial, as  a  regular  and  gentle  horizontal  motion  is  indispensable 
to  insure  uniformity  and  impalpability.  Some  substances,  how- 
ever, as  magnesia,  &c.,  which  obstruct  the  pores  of  the  cloth, 
must  be  forced  through  in  this  manner,  and  even,  if  necessary, 
by  a  circular  motion  of  the  fingers  over  the  interior  surface  of 
the  cloth.  This  manipulation  frees  the  meshes  of  the  cloth  from 
obstructions,  but  it  must  be  carefully  done,  otherwise  the  safety 
of  the  cloth  will  be  endangered.  A  sieve  is  also  useful  for  the 
admixture  of  powders  of  uniform  fineness. 

The  importance  of  restricting  the  sieve  to  a  horizontal  motion 
induced  Mr.  Harris,  of  Philadelphia,  to  invent  a  special  ar- 
rangement (Fig.  69)  for  the  purpose.  The  sieve  is  of  the  usual 
form,  but  requires  to  be  enclosed  in  a  box.  Motion  is  communi- 
cated by  means  of  a  wheel,  an  axle,  and  a  crank,  with  six  eccentric 
depressions  and  elevations 

upon  one  of  its  sides.    There  Fi?.  69. 

are  two  upright  standards 
fastened  to  the  same  foot- 
board, one  of  which  supports 
the  wheel  and  the  other  a 
horizontal  bar  of  iron  pass- 
ing through  the  side  of  the 
box  and  attached  by  the 
other  end  to  the  side  of  the 
sieve,  resting  on  horizontal 
ledges  in  the  interior  of  the 
box.  On  turning  the  crank, 
the  horizontal  bar  will,  in 

its  motion,  necessarily  follow  the  sinuosities  of  the  wheel,  and  as 

7 


98  LEVIGATION. 

a  consequence  draw  the  sieve  backwards  and  forwards.  Very 
fine  powders  are  obtained  by  enclosing  the  powdered  matters  in 
a  bag  of  close  texture  and  shaking  it  within  a  tin  canister,  which 
catches  and  retains  the  dust  as  it  passes  through  the  meshes. 

7th.  Levigation — Is  that  mode  of  mechanical  reduction  which 
is  practised  by  first  rubbing  the  substance  into  a  smooth  paste, 
and  then  separating  the  finer  from  the  coarser  portions  by  agita- 
ting the  triturated  matters  with  water.  After  a  sufficient  repose, 
the  grosser  and  heavier  portions  subside,  leaving  the  lighter  par- 
ticles still  suspended  in  the  water.  This  water,  after  decantation, 
gives  a  second  deposit  of  an  increased  state  of  fineness.  The 
third  or  fourth  decantation  yields  the  powder  of  impalpable  fine- 
ness. The  time  of  repose  between  the  decantations,  unless  great 
impalpability  is  required,  should  be  limited,  and  only  long  enough 
to  allow  the  deposition!  of  the  heavier  portions.  The  coarse  pre- 
cipitates are  collected  together,  a  second  and  as  many  more  times 
as  necessary,  rubbed  up  as  before,  and  treated  with  water,  until 
all  the  lighter  portions  have  been  separated.  This  process  ap- 
plies only  to  substances  unalterable  by  wrater.  When  uniformity 
of  fineness  is  not  all-important,  one  washing  even  suffices,  and 
can  be  accomplished  in  the  mortar  without  the  use  of  glasses. 
Alternate  poundings  and  washings  will  eventually  reduce  and 
remove  the  whole  contents  of  the  mortar.  In  washing  over  gold 
and  other  metallic  ores,  where  only  the  heavier  portions  are  to 
be  reserved,  the  water  may  be  allowed  to  flow  directly  into  the 
mortar,  which  being  held  in  an  inclined  position,  permits  its  exit, 
together  with  the  fine  dusty  portions  which  are  kept  in  suspension 
by  trituration  with  the  pestle. 

This  process  of  levigation  is  founded  upon  the  different  specific 
gravities  of  the  coarse  and  fine  bruised  matters,  and  is,  therefore, 
not  only  applicable  for  the  separation  of  the  particles  of  homo- 
geneous matters,  but  also  of  equally  fine  matters  of  unequal  den- 
sities. In  the  latter  case  it  takes  the  name  of  elutriation. 

All  minerals  for  analysis,  which  have  to  undergo  ignition  with 
alkalies,  should  be  previously  levigated,  in  order  that  decompo- 
sition may  be  complete ;  for  if  the  powder  is  not  uniform  the 
larger  particles  will  escape  decomposition. 

Pulverization  in  this  manner,  by  uniformly  comminuting  the 
particles,  promotes  their  equal  expansion  and  the  escape  of  con- 


GRANULATION.  99 

tained  moisture,  and  thus  prevents  the  decrepitation  of  substances 
when  heated. 

The  deposited  powder  must  always  be  dried,  by  exposure,  pre- 
vious to  subjecting  it  to  any  other  process. 

8th.  Reduction  by  Granulation. — The  reduction  of  metals  to 
granules  is  effected  by  fusing  them  in  a  crucible,  and  pouring  the 
melted  matter,  from  an  elevation,  in  a  thin  stream,  very  gradu- 
ally, into  a  large  bulk  of  cold  water  which  must  be  kept,  during 
the  process,  in  constant  agitation  with  a  stirrer.  The  fineness  of 
the  resultant  granules  is  proportional  to  the  slowness  with  which 
the  fused  metal  was  poured  into  the  water.  It  is  more  convenient 
to  transfer  the  metal  from  the  crucible  into  a  ladle,  and  project 
it  into  the  water  from  that  more  handy  vessel,  which  enables  a 
frequent  change  of  the  position  of  the  descending  stream,  and 
thus  prevents  the  formation  of  clots  instead  of  smaller  and  more 
solid  granules.  The  fusion  of  zinc  for  granulation  must  be  in  a 
covered  crucible,  otherwise  it  becomes  oxidized  whilst  hot,  and 
partially  sublimes  by  exposure  in  an  open  vessel.  Zinc  and  tin 
may  also  be  finely  divided  by  heating  them  a  little  above  their 
melting-points  and  rubbing  them  in  a  previously  heated  iron 
mortar,  until  the  mass  congeals  into  powder.  Iron  is  brought  to 
powder  mechanically  by  the  file,  and  chemically  by  reduction  in 
an  atmosphere  of  hydrogen  gas. 

The  process  of  fusing  metals  and  then  agitating  the  melted 
matter  in  a  wooden  box  until  cool,  reduces  them  to  a  state  of 
minute  division,  but  at  the  same  time  promotes  their  oxidation. 
For  general  purposes,  however,  it  is  not  objectionable,  and  the 
particles  of  charred  wood  with  which  it  becomes  mixed  can  be 
separated  by  elutriation.  The  sides  of  the  box  are  generally 
well  chalked,  to  prevent  any  adherence  of  the  metal; — and  this 
also  is  separable  by  elutriation. 

REDUCTION   BY   CHEMICAL   MEANS. 

9th.  Division  by  Intermedia. — This  mode  is  both  mechanical 
and  chemical,  and  applies  particularly  to  the  noble  metals,  in 
foil,  which  are  difficult  of  pulverization.  Honey,  sugar,  salts, 
&c.,  are  the  most  usual  media.  By  binding  the  particles  together, 
it  assists  their  minute  division,  and  prevents  their  escape  from 


100  THE  BALANCE. 

the  mortar.  The  addition  of  boiling  water  solves  out  the  medium, 
without  action  upon  the  metallic  powder,  which  then  only  requires 
to  be  thrown  upon  a  filter  and  dried. 

Phosphorus  may  be  finely  divided  by  fusing  it,  with  alcohol, 
over  a  water-bath,  and  shaking  the  contents  of  the  flask  until 
thoroughly  cooled.  The  phosphorus  subsides  at  the  bottom  in 
pulverulent  form.  Camphor,  which  is  obstinate  under  the  pestle, 
readily  yields  to  its  power  when  mixed  with  a  few  drops  of  alco- 
hol or  ether,  to  destroy  its  elasticity. 

Silica  may  be  precipitated  from  lime-glass  in  a  pulverulent 
form,  by  the  digestion  of  that  compound  with  hydrochloric  acid. 
Silver  is  obtained  in  a  powder  by  the  decomposition  of  its  nitric 
solution  with  a  metallic  copper  rod ;  or  of  its  chloride  by  metallic 
zinc.  Proto-sulphate  of  iron  throws  down  gold,  in  a  finely-divided 
state,  from  the  solution  of  its  chloride;  and  spongy  platinum  is 
formed  by  the  dull  ignition  of  the  ammonia-chloride  of  that  metal. 
These  are  instances  of  chemical  division  by  purely  chemical 
means.  The  extreme  state  of  division  thus  obtained  by  the 
solution  and  precipitation  of  a  solid  body,  (a  chemico-mechanical 
process)  cannot  be  effected  by  any  purely  mechanical  power. 

The  sublimation  of  sulphur  into  flowers,  as  also  of  calomel  into 
fine  powder  by  means  of  large  airy  chambers,  are  instances  of 
comminution  by  chemico-mechanical  means ; — the  vaporized  par- 
ticles being  prevented  from  reunion,  at  the  moment  of  solidifica- 
tion, by  the  intervention  of  the  cold  air.  So,  likewise,  in  cases 
of  division  by  hydro-sublimation,  the  intervention  of  aqueous 
vapor  prevents  the  conjunction  of  the  vaporized  molecules.  Dr. 
Joslin  (Sillimaris  Journal,  p.  48,  vol.  v)  treats  of  this  subject  in 
extenso. 


CHAPTER  V. 

THE   BALANCE. 


A  BALANCE  may  be  considered  the  most  indispensable  imple- 
ment of  the  laboratory,  as  affording  the  only  means  by  which  the 
chemist  can  accurately  estimate  the  quantitative  results  of  his  in- 


THE   BALANCE — ITS   REQUISITE   CONDITIONS.  101 

vestigations.  The  construction  of  this  instrument  for  determining 
the  relative  weight  (the  measure  of  the  force  by  which  any  body, 
or  a  given  portion  of  it,  gravitates  towards  the  earth)  of  sub- 
stances, is  based  upon  certain  mechanical  principles,  of  which  we 
proceed  to  give  a  brief  explanation. 

A  balance  consists  of  an  upright  shaft,  supporting,  by  its 
immediate  centre,  an  inflexible  lever  or  beam,  with  arms  of  equal 
length  and  symmetry,  to  each  of  which  is  suspended  a  dish  for 
the  reception  of  the  weights  (the  power),  and  the  body  to  be 
weighed  (the  resistance).  Of  the  three  axes  of  the  beam,  that  in 
the  middle  is  the  fulcrum  or  centre  of  motion,  upon  which  it 
turns  in  a  vertical  plane.  The  other  two  axes  are  at  the  extre- 
mities of  the  arms.  All  three  axes  should  be  at  right  angles  to 
the  plane  of  motion,  and  parallel  to  each  other. 

The  requisite  conditions  of  a  good  balance. — One  of  the  chief 
conditions  of  an  accurate  balance  is  a  free  suspension  of  the 
beam,  in  order  that  it  may  vibrate  with  the  least  possible  friction. 
The  two  arms  must  also  be  precisely  equal,  so  that  when  empty, 
or  the  weight  in  each  dish  is  uniform,  there  will  be  a  perfect 
equilibrium.  The  sensibility  of  a  balance  is  proportional  to  the 
angle  formed  by  the  beam  with  the  horizon,  when  a  slightly 
greater  weight  is  placed  in  one  dish  than  in  the  other.  This 
sensibility  depends  on  the  position  of  the  centre  of  gravity  of  the 
beam  with  reference  to  the  line  of  suspension ;  this  centre  must 
be  below  that  line,  but  as  near  as  possible  to  it,  so  that  the 
slightest  weight  will  cause  the  beam  to  oscillate  freely. 

As  the  inertia  and  friction  are  proportional  to  the  weight  of 
the  beam,  it  must  be  made  of  material  entirely  free  from  imper- 
fections, and  so  as  to  combine  strength  and  inflexibility  with 
lightness.  It  may  be  of  solid  steel,  rolled  brass,  German  silver, 
or  of  a  malleable  alloy  of  copper  and  tin,  but  not  of  cast  metal 
of  any  kind.  The  upright  support  can  be  of  brass,  and  the 
dishes  and  suspension  frames  of  platinum. 

The  sensibility  of  the  balance  increases  with  the  length  of  the 
arms,  which  should,  however,  have  a  certain  limit,  and  be  as 
nearly  uniform  as  possible  in  every  respect.  When,  through 
unskilful  construction,  the  length  of  one  arm  is  slightly  greater 
than  that  of  the  other,  in  order  to  avoid  the  error  in  weighing 
which  this  defect  would  occasion,  the  body  to  be  weighed  is 


102  THE    MINT   BALANCE. 

placed  in  one  pan,  and  counterbalanced  by  weights  in  the  other. 
The  amount  of  weight  required  to  restore  the  equilibrium,  after 
the  withdrawal  of  the  substance,  is  its  correct  weight. 

In  order  to  avoid  friction,  the  parts  of  contact  should  be  as 
few  as  possible,  and  the  knife  edges  must  be  made  of  highly 
polished,  hardened  steel,  and  the  beds  or  planes  upon  which  they 
rest,  of  agate  or  flint.  The  accuracy  of  the  balance  will  depend 
greatly  upon  the  skill  and  precision  with  which  these  portions 
and  the  beam  are  elaborated. 

A  good  balance,  with  1  to  2000  grains  on  each  dish,  should  be 
sensitive  to  the  one  or  two  thousandth  of  a  grain. 

The  Mint  Balance. — "  To  obtain  the  greatest  degree  of  uni- 
form precision,  it  is  requisite  that  the  beam  should  be  lifted  from 
a  state  of  rest,  in  a  perfectly  level  position,  and  that  the  stirrups 
should  be  lifted  simultaneously  with  their  loads  from  their  rests 
or  supports;  also  that  the  oscillations  of  the  stirrups  should 
be  prevented  or  checked  at  the  earliest  moment;  and,  finally, 
that  the  whole  system  should  be  left  at  liberty  with  delicacy  and 
exactitude,  so  as  to  remain  in  equilibrium,  or  vibrate  as  the  case 
may  be." 

"  To  command  the  above  conditions,  the  beam  should  be  sup- 
ported upon  cones  at  each  extremity,  adjusted  level  with  each 
other,  from  which  it  is  lifted,  by  a  plane  (and  not  a  portion  of  a 
hollow  cylinder,  as  is  usual),  which  rises  under  its  centre  knife- 
edge,  and  to  which  it  is  returned  by  its  depression,  the  cones 
guiding  the  beam  to  the  same  position  exactly  from  which  it  was 
elevated. 

"  The  stirrups,  in  like  manner,  should  hang  upon  hollow  cones 
or  V's,  so  as  to  be  taken  up  from,  and  returned  invariably  to  the 
same  position. 

"  The  beam  should  rest  upon  its  cones,  and  the  stirrups  should 
be  supported  by  their  V's  at  such  heights  as  to  relieve  entirely 
the  knife-edges,  with  a  sufficient  space  between  them  and  their 
respective  planes  to  permit  inspection  and  wiping,  when  it  may 
be  needed.  This  construction  admits  of  the  placing  of  the 
weights,  &c.,  and  guards  the  knife-edges  from  the  consequences 
of  displacement  during  use.. 

"  The  beam  should  be  raised  by  the  elevation  of  the  centre 
plane,  subsequently  lifting  with  it  the  stirrups  with  their  weights 
and  load,  and  all  oscillation  checked  by  platforms  placed  in  the 


THE    MINT   BALANCE. 


103 


table  under  the  centre  of  the  stirrups,  which  should  be  made  to 
rise  simultaneously,  and  should  be  counter-weighed  to  the  requi- 
site delicacy. 

"  The  descent  of  these  platforms,  effected  by  the  pressure  of 
a  finger  on  a  lever  conveniently  placed,  will  leave  the  stirrups, 
&c.,  at  liberty  to  vibrate,  or  bring  the  beam  to  a  horizontal  position, 
at  the  will  of  the  operator,  being  a  convenient,  certain,  and  rapid 
method  of  manipulating,  not  equalled  by  any  other  arrangement, 
and,  in  fact,  essential  to  a  well-constructed  balance." 

These  essential  qualities  of  an  accurate  balance  for  the  more 
delicate  operations  of  the '  laboratory  are  comprised  in  that  form 
of  balance  used  in  the  United  States  Mint,  and  which  "  combines 
all  the  important  advantages  heretofore  known  with  such  im- 
provements as  have  been  the  growth  of  their  own  experience." 

This  form  of  balance  is  best  adapted  for  exact  weighings  of 
large  quantities  of  matter ;  and  therefore  should  constitute  the 
larger  weighing  apparatus  of  the  laboratory. 

Fig.  TO  gives  a  front  view  of  it.  We  take  our  description  from 
the  Journal  of  the  Franklin  Institute,  vol.  xiv. 

Fig.  70. 


A  table,  marked  A,  is  furnished  with  levelling  screws  upon  the 
front  and  back  edge,  and  at  each  end,  marked  b.  In  Fig.  72, 
which  exhibits  different  views  of  all  the  parts,  the  levelling  screws 
are  marked  5,  and  their  positions  in  the  table  (the  view  of  the 
under  side  of  which  is  given)  are  marked  c. 

The  balance  is  intended  to  be  placed  upon  a  counter,  or  any 


104 


THE    MINT   BALANCE. 


other  firm  support,  and  the  table  levelled  by  means  of  the  screws 
last  described,  its  true  position  being  indicated  by  a  plumb-line 
and  weight  occupying  the  rear  opening  in  the  column  (Fig.  72, 
C) ;  the  plumb-line  and  weight  being  marked  d. 

The  column,  marked  C,  Figs.  70,  72,  contains  the  lifting  ap- 
paratus, and  supports  the  cap-plate,  marked  D.  The  cap-plate 
guides  the  lifting  apparatus,  and  supports  the  V's,  or  hollow 
cones,  for  the  stirrups,  and  is  strengthened  and  stayed  by  braces, 
marked  E  ;  the  section  of  which  braces  is  cruciform,  with  circular 
ends,  for  firm  bearing  upon  the  plate  and  base  of  the  column,  to 
which  they  are  secured  by  screws. 

Figs.  71,  72,  exhibit  upper  and  under  views  of  the  table,  co- 
lumn, plate,  &c.,  also  upper  and  lower  end  views  of  the  column, 
showing  the  means  of  its  attachment  to  the  table  and  cap-plate. 

Fig.  71. 


The  lifting  apparatus  consists  of  a  winch-handle,  marked  /, 
Fig.  72,  fitting  upon  a  round  shaft  #,  with  a  feather,  so  as  to 
admit  of  its  convenient  removal;  upon  this  shaft  is  fitted  a  cam 
A,  also  secured  by  a  feather ;  the  cam  is  carefully  constructed, 
so  as  to  give  equal  elevation  to  equal  parts  of  its  revolution ;  and 
upon  the  cam  rests  a  roller  i,  which  turns  upon  a  pin  in  the 
frame  /,  intended  to  reduce  friction,  and  give  facility  in  raising 
the  beam  with  its  load. 

The  lifting  frame  /,  is  forked  cross-wise,  so  as  to  straddle  the 
shaft  and  accommodate  the  cam  and  roller,  at  the  same  time  that 
it  allows  the  necessary  vertical  motion,  without  the  possibility  of 
being  displaced ;  all  of  which  is  exhibited  in  the  two  views  of  the 


THE    MINT    BALANCE.  105 

lifting  frame  marked  j,  which  is  also  accompanied  by  sections  in 
proximity  to  the  parts  which  they  are  intended  to  explain. 

The  handle  is  so  placed  as  to  be  on  the  left  when  the  beam  is 
down  and  at  rest,  and  to  the  right  when  the  beam  is  raised,  in  the 
act  of  weighing,  and  makes,  together  with  the  cam,  more  than 
three-fourths  of  a  revolution,  the  cam  having  a  very  slight  de- 
pression upon  its  upper,  or  highest  point,  into  which  the  roller 
falls,  maintaining  it  in  its  position  when  the  beam  is  raised.  It 
is  then  extended  beyond  the  centre  of  the  roller,  so  as  to  be 
stopped  at  the  limit  of  motion,  as  exhibited  A,  Fig.  72. 


Fig.  72. 


s     "^  >i©*   H    13 


The  lifting-frame  is  forked  at  the  top  for  the  accommodation 
of  the  beam.  Upon  it  rests  the  plane,  the  top  and  side  view  of 
which  are  marked  k,  for  the  support  of  the  centre  knife-edge, 
secured  to  the  frame  by  screws.  In  balances  of  ordinaryt  con- 
struction, this  plane  may  be  made  of  hardened  cast-steel ;  in  finer 
instruments,  of  bronze,  or  brass,  with  an  inserted  block  of  polished 
agate,  secured  by  fusible  metal  or  cement. 

The  position  of  the  handle,  lifting-frame,  &c.,  are  exhibited 
with  sufficient  clearness  in  the  front  view,  Fig.  70. 

The  cap-plate,  views  of  the  upper  and  under  sides  of  which  are 
given  at  D,  Fig.  71,  is  constructed  with  horizontal  spaces  at  the 
centre  and  each  end.  In  the  middle  it  is  secured  to  the  column 
by  four  screws,  and  to  the  braces  B  in  the  same  manner,  the 
holes  for  which  are  marked  in  all  the  views. 

The  square  opening  in  the  middle  serves  as  a  guide  and  sup- 
port to  the  lifting-frame,  which  must  be  accurately  fitted,  so  as 
to  prevent  any  lateral  play. 


106  THE   MINT   BALANCE. 

The  horizontal  spaces  at  the  extremity  of  the  cap-plate  support 
short  pillars  terminated  by  cones,  upon  which  the  beam  rests ; 
these  pillars  are  secured  to  the  cap-plate  by  screws  passing 
through  it  from  the  under  side,  the  holes  through  which  they 
pass  being  large  enough  to  admit  of  the  adjustment  of  the  beam 
to  its  proper  place,  previous  to  their  being  permanently  fastened 
down. 

The  details  of  these  pillars  are  given  at  ?,  Fig.  72,  the  cones 
being  constructed  of  cast  steel,  hardened  and  polished. 

The  same  space  also  supports  the  V's,  or  guide  supports  of  the 
hangers,  different  explanatory  views  of  which  are  given  in  Fig. 
72,  the  V's  being  marked  m9  and  the  hangers  n.  All  these 
parts  have  been  devised  with  reference  to  the  simplest  and  most 
economical  construction  consistent  with  the  requisite  accuracy, 
and  for  affording  the  greatest  facility  in  the  final  adjustment  of 
the  balance. 

The  most  important  part  of  the  balance  is  the  beam  o ;  and  Fig. 
72  exhibits  side  and  top  views.  The  projections  marked  <?,  are 
the  supports  of  the  beam  when  at  rest ;  the  conical  cavities,  indi- 
cated by  dotted  lines,  being  made  to  fit  the  cones  marked  I. 

This  form  of  beam  affords  facility  in  construction,  being  com- 
posed of  straight  surfaces,  without  ribs  or  curves ;  is  well  adapted 
to  maintain  its  form  when  loaded :  affords  the  least  surface  for 
accumulation  of  dust,  and  is  readily  wiped  when  it  may  be 
necessary.  The  means  of  adjustment  for  the  length  of  arm  is 
exhibited  at  r,  Fig.  72. 

It  will  be  seen,  that  the  needle  of  the  balance  which  is  the 
subject  of  description,  is  pointed  downwards ;  and  there  are  good 
reasons  for  this  disposition,  In  the  first  place  it  is  directly 
before  the  eye  of  the  operator,  and,  therefore,  more  convenient 
in  use,  than  it  is  when  elevated  above ;  again,  it  may  be  made 
longer  than  the  arms  of  the  beam,  and  will,  consequently,  de- 
scribe a  larger  arc,  and  thus  give  more  distinct  indications, 
whilst  the  whole  arrangement  need  occupy  no  more  space  than  is 
requisite  for  the  other  parts ;  and,  finally,  the  needle  is  protected 
from  external  injury  by  the  lifting-frame  and  column,  in  the 
centre  of  which  it  is  placed* 

The  parts  which  remain  to  be  described  have  been  usually 
considered  of  minor  importance,  but  experience  has  shown  that 


THE   MINT   BALANCE.  107 

this  estimate  is  scarcely  a  just  one,  inasmuch  as  they  afford  faci- 
lities for  accuracy  and  rapidity,  that  leave  no  doubt  of  their  value, 
and  place  them  in  a  most  important  position  in  practice.  The 
parts  now  alluded  to,  constitute  the  system  by  which  the  opera- 
tor is  enabled  to  find  the  equilibrium  of  which  he  is  in  search.  It 
consists  of  the  pedestals,  as  they  have  been  termed,  marked  s, 
Figs.  70  and  71,  and  the  parts  connected  with  them,  marked  t, 
u,  v,  and  w,  in  Fig.  71 ;  a  light  shaft,  made  of  tubular  iron,  £, 
supported  by  pivots  w,  which  pivots  are  screwed  through  a  piece 
cast  on  the  under  side  of  the  table,  marked  V ;  upon  the  ends  of 
this  shaft  there  are  levers  W,  upon  the  ends  of  which  levers,  when 
in  place,  the  pedestals  rest. 

The  remaining  part  of  this  system  is  a  double  armed  lever, 
placed  in  the  middle  of  the  shaft  t  (represented  in  the  engraving 
detached),  and  marked  x ;  it  is  connected  by  a  pin,  with  the 
trigger,  z,  represented  in  its  place  in  Fig.  71,  with  the  same 
letter.  Upon  the  other  end  of  the  lever  x,  there  is  a  weight  #, 
capable  of  adjustment  by  a  screw  upon  which  it  traverses,  so  that 
it  may  be  made  to  approach,  or  recede  from  the  shaft  t. 

The  action  of  this  system  is  easily  understood;  its  whole  ob- 
ject is  to  depress  the  platforms  by  sufficient  force,  applied  by  the 
finger,  to  the  trigger,  the  counter-weight  returning  them  to  their 
original  position,  after  its  removal. 

It  will  be  seen,  by  reference  to  Fig.  70,  that  the  under  sides 
of  the  stirrups  have  a  space,  represented  by  dotted  lines,  in  which 
the  platforms  are  placed,  which  allows  the  stirrups  to  oscillate 
within  its  limits,  but  beyond  which  they  cannot  move.  This  con- 
struction is  intended  to  guard  the  hangers  from  displacement, 
and  to  prevent  injury  by  too  much  movement  of  the  stirrups,  an 
accident  very  likely  to  occur,  when  the  pans  or  weights  are 
hastily  removed,  especially  in  the  use  of  heavy  weights  or  large 
masses. 

The  cavity,  whose  object  was  described  in  the  last  paragraph, 
forming  the  under  side  of  the  base  of  the  stirrups,  is  turned  as 
truly  as  possible  in  the  form  of  a  portion  of  a  sphere,  whose 
radius  is  its  distance  from  the  bearing  of  the  knife-edge.  The 
platforms  are  adjusted  by  means  of  the  counter-weight,  so  as  to 
press  lightly  up  against  the  stirrups,  and  to  follow  them  when 
raised. 


108  EATER'S  BALANCE, 

It  is  found  convenient  in  practice  to  turn  the  handle  of  the 
balance  but  a  small  portion  of  its  movement,  if  the  weights  are 
not  equal  on  opposite  sides,  a  circumstance  to  be  expected  \vhen 
searching  for  a  weight.  The  heavy  side  will  remain  down,  and 
the  needle  will  indicate  whether  addition  of  weight  or  its  removal 
is  requisite.  These  trials  are  continued  until  the  platforms  fol- 
low up  the  whole  lift,  the  needle  remaining  opposite  the  middle 
line  of  its  scale,  until  the  handle  is  stopped  by  its  limit  of  motion, 
where  it  remains.  The  finger,  then,  by  pushing  down  the  trig- 
ger, will  depress  the  platforms,  when  smaller  weights  are  em- 
ployed, until  the  needle  indicates  equilibrium. 

In  this  balance  there  is  little  or  no  embarrassment  from  oscil- 
lation, because  the  stirrups  immediately  accommodate  themselves 
to  the  position  of  the  weights,  the  light  pressure  permitting  them 
to  take  any  position  required  by  the  load ;  nevertheless,  having 
sufficient  power,  from  their  pressure,  to  prevent  any  swinging. 
If  from  any  cause  the  stirrups  should  be  in  motion,  three  conse- 
cutive depressions  of  the  platforms  will  bring  them  to  a  state  of 
rest  with  absolute  certainty,  and  with  a  loss  of  time  so  short  as 
to  be  entirely  immaterial. 

The  stirrups  are  connected  with  the  hangers,  by  a  rod,  which 
is  double-jointed,  as  near  to  the  hangers  as  possible,  so  as  to 
allow  perfect  freedom  of  motion  ;  at  the  same  time,  so  well  fitted 
as  to  allow  no  change  of  position  in  the  parts.  On  the  lower 
ends  of  these  rods  there  are  screws  and  nuts,  to  regulate  the 
height  of  the  stirrups,  together  with  a  jam-nut,  to  prevent  any 
change  after  the  adjustment  has  been  satisfactorily  made. 

The  bases  of  the  stirrups  are  designedly  made  small,  requiring 
the  use  of  a  dish  on  the  one  side,  and  a  platform  for  weights  on 
the  other.  This  dish  and  platform  being  made  of  equal  weight, 
renders  the  use  of  a  counter-weight  unnecessary ;  and  as  the 
balance  cannot  be  used  without  both,  the  liability  to  mistakes 
from  this  cause  is  entirely  avoided. 

The  principle  of  the  Mint  balance  has  been  adopted  in  the 
construction  of  one  of  our  finest  analytical  balances,  which  was 
made  for  us  by  John  Jones,  Baltimore. 

Hater's  and  Robinson's  .balance.  This,  Fig.  73,  though  more 
complicated  than  the  preceding,  is  an  excellent  balance  for  estima- 
ting minute  quantities  with  precision ;  and,  indeed,  for  all  the 


ROBINSON'S  BALANCE. 


109 


weighing  operations  of  delicate  research.     When  carefully  pre- 
served, it  retains  its  sensibility  for  many  years. 

Fig.  73. 


We  are  indebted  for  our  description  to  Lardners  Elements  of 
Mechanics. 

"  The  beam  of  this  balance  is  only  ten  inches  long.  It  is  a 
frame  of  bell-metal  in  the  form  of  a  rhombus.  The  fulcrum  is 
an  equilateral  triangular  prism  of  steel,  one  inch  in  length ;  but 
the  edge  on  which  the  beam  vibrates  is  formed  to  an  angle  of 
120°,  in  order  to  prevent  any  injury  from  the  weight  with  which 
it  may  be  loaded.  The  chief  peculiarity  in  this  balance  consists 
in  the  knife-edge,  which  forms  the  fulcrum,  bearing  upon  an 
agate  plane  throughout  its  whole  length ;  whereas  in  the  other 
balances  the  whole  weight  is  supported  by  portions  only  of  the 
knife-edge,  amounting  together  to  one-tenth  of  an  inch.  The 
supports  for  the  scales  are  knife-edges,  each  six-tenths  of  an  inch 
long.  These  are  each  furnished  with  two  pressing-screws,  by 
means  of  which  they  may  be  made  parallel  to  the  central  knife- 
edge.  , 

"Each  end  of  the  beam  is  sprung  obliquely  upwards  and 
towards  the  middle,  so  as  to  form  a  spring  through  which  a 


110  ROBINSON'S  BALANCE. 

pushing-screw  passes,  which  serves  to  vary  the  distance  of  the 
point  of  suspension  from  the  fulcrum,  and,  at  the  same  time,  by 
its  oblique  action,  to  raise  or  depress  it,  so  as  to  furnish  a  means 
of  bringing  the  points  of  suspension  and  the  fulcrum  into  a  right 
line. 

"  A  piece  of  wire,  four  inches  long,  on  which  a  screw  is  cut, 
proceeds  from  the  middle  of  the  beam  downwards.  This  is 
pointed  to  serve  as  an  index,  and  a  small  brass  ball  moves  on  the 
screw,  by  changing  the  situation  of  which  the  place  of  the  centre 
of  gravity  may  be  varied  at  pleasure. 

"  The  fulcrum,  as  before  remarked,  rests  upon  an  agate  plane 
throughout  its  whole  length,  and  the  scale-pans  are  attached  to 
planes  of  agate,  which  rest  upon  the  knife-edges,  forming  the 
points  of  support.  This  method  of  supporting  the  scale-pans, 
we  have  reason  to  believe,  is  due  to  Mr.  Cavendish.  Upon  the 
lower  half  of  the  pillar,  to  which  the  agate  plane  is  fixed,  a  tube 
slides  up  and  down  by  means  of  a  lever  which  passes  to  the  out- 
side of  the  case.  From  the  top  of  this  tube,  arms  proceed 
obliquely  towards  the  ends  of  the  balance,  serving  to  support  a 
horizontal  piece,  carrying  at  each  extremity  two  sets  of  Y's,  one 
a  little  above  the  other.  The  upper  Y's  are  destined  to  receive 
the  agate  planes  to  which  the  scale-pans  are  attached,  and  thus 
to  relieve  the  knife-edges  from  their  pressure ;  the  lower  to 
receive  the  knife-edges  themselves,  which  form  the  points  of 
suspension  of  the  pans,  consequently  these  latter  Y's,  when  in 
action,  sustain  the  whole  beam. 

"  When  the  lever  is  freed  from  a  notch  in  which  it  is  lodged, 
a  spring  is  allowed  to  act  upon  the  tube  we  have  mentioned,  and 
to  elevate  it.  The  upper  Y's  first  meet  the  agate  planes  carry- 
ing the  scale-pans,  and  free  them  from  the  knife-edges.  The 
lower  Y's  then  come  into  action,  and  raise  the  whole  beam,  ele- 
vating the  central  knife-edge  above  the  agate  plane.  This  is  the 
usual  state  of  the  balance  when  not  in  use:  when  it  is  to  be 
brought  into  action,  the  reverse  of  what  we  have  described  takes 
place.  On  pressing  down  the  lever,  the  central  knife-edge  first 
meets  the  agate  plane,  and  afterwards  the  two  agate  planes, 
carrying  the  scale-pans,  are  deposited  upon  their  supporting 
knife-edges. 

"A  balance  of  this  construction  was  employed  by  Captain 


BERLIN   BALANCE. 


Ill 


Kater  in  adjusting  the  national  standard  pound.  With  a  pound 
troy  in  each  scale,  the  addition  of  one-hundredth  of  a  grain 
caused  the  index  to  vary  one  division,  equal  to  one-tenth  of  an 
inch  ;  and  Mr.  Robinson  adjusts  these  balances  so  that  with  one 
thousand  grains  in  each  scale,  the  index  varies  perceptibly  on  the 
addition  of  one-thousandth  of  a  grain,  or  of  one-millionth  part  of 
the  weight  to  be  determined." 

Duffy  has  added  a  very  simple  but  useful  improvement.  It 
consists  of  an  elastic  spring, 
A  A,  Fig.  74,  serving  as  a  sup- 
port for  the  dishes  when  the  ba- 
lance is  at  rest;  and  at  the 
same  time  so  arranged,  that  by 
the  depression  of  the  thumb- 
lever  suitably  attached,  the  dishes  are  thrown  off  their  supports, 
and  the  beam  put  into  action  simultaneously. 

Fig.  75. 


Fig.  74. 


Berlin  Balance. — This  pattern  of  balance  combines,  in  an 
eminent  degree,  all  the  requirements  of  a  convenient  and  exact 
weighing  apparatus  at  a  moderate  cost.  It  is,  therefore,  deserv- 


112  BERLIN   BALANCE. 

edly  popular  with  chemists  for  the  analytical  and  delicate  weigh- 
ings of  the  laboratory.  Fig.  75  presents  the  instrument  in  its 
most  improved  form. 

The  support  and  beam  are,  as  usual,  of  brass;  the  pans  of 
platinized  copper,  and  the  suspension  wires  of  the  same  material, 
or  pure  platinum.  The  beam  is  constructed  with  knife-edges  at 
the  ends,  and  upon  which  the  pans  are  suspended  by  agate  planes. 
The  centre  knife-edge  also  moves  upon  an  agate  plane ;  and  to 
bring  all  the  knife-edges  into  the  same  straight  line  as  well  as  to 
equalize  the  lengths  of  the  arms  of  the  beam,  the  latter  is  fitted 
with  a  suitable  means  of  adjustment.  A  screw-knob  above  the 
centre  of  the  beam  serves  to  adjust  the  centre  of  gravity. 

The  balances  are  made  either  with  or  without  supports  to  the 
pans,  as  may  be  preferred  by  the  operator ;  but,  in  either  case, 
there  is  a  mechanical  system  for  steadying  them.  It  connects 
with  the  same  axis  which  moves  the  beam,  so  that  one  movement 
of  the  handles  first  releases  the  pans  and  then  the  beam.  When 
supports  are  used,  they  must  be  faced  with  ivory  to  prevent  the 
pans  losing  any  weight  by  abrasion  of  their  under  surfaces. 

The  beam  is  graduated  on  each  arm  into  ten  divisions,  for  the 
use  of  a  sliding-weight  or  "rider;"  and  an  apparatus  above  the 
beam,  at  the  right  side,  serves,  by  means  of  an  external  handle 
or  knob,  for  moving  the  rider  from  division  to  division,  as  may  be 
necessary,  without  opening  the  case.  The  use  of  the  rider,  as 
will  be  learned  in  the  chapter  on  WEIGHING,  does  away  with  the 
necessity  of  having  weights  lower  than  the  hundredth  of  a  grain 
or  a  centigramme. 

These  balances  are  generally  provided  with  the  supplementary 
apparatus  for  taking  specific  gravities  and  for 
weighing  tubes,  bulbs,  &c.  (Fig.  76).  The 
lantern,  or  glass  case,  is  constructed  with  ad- 
justing screws  to  maintain  a  perfect  level ; 
and  the  drawers  at  the  bottom  being  fitted 
with  plush-covered  receptacles  for  the  several 
parts  of  the  apparatus,  it  becomes  a  safe 
means  of  transporting  the  instrument  without 
the  trouble  of  special  packing.  The  sliding 
part  and  back,  and  the  hinged  doors  at  the 
end,  afford  every  facility  for  weighing  long 


TRALLE'S  BALANCE.  113 


tubes  and  similar  apparatus;  and  in  the  finer  balances,  the  bot- 
tom is  of  glass-plate,  which  contributes  materially  to  the  good 
order  of  the  balance,  as  it  may  be  readily  kept  clean.  These  ba- 
lances cost  $30,  $60,  $90,  and  $125,  according  to  finish,  and 
inclusive  of  weights.  Those  at  the  lowest  prices  will  carry  four 
hundred  grains,  and  turn  with  one-fiftieth  of  a  grain.  Those  of 
greatest  delicacy  will  turn  with  one-thousandth  of  a  grain  when 
loaded  with  fifteen  hundred  grains. 

Assay  Balance. — This  instrument  should  be  constructed  with 
great  skill  and  accuracy ;  for  it  is  used  only  for  the  very  precise 
weighing  of  minute  quantities.  When  the  luxury  can  be  afforded, 
the  laboratory  should  be  provided  with  one ;  but  otherwise  the 
analytical  balance  may  be  made  to  serve  its  purposes.  To  this 
end,  it  must  always  be  kept  in  perfect  adjustment.  For  blow- 
pipe operations,  Plattner's  Assay  Balance  will  be  found  very  satis- 
factory. If  skilfully  made,  it  will  turn  with  one-fifth  of  a  milli- , 
gramme ;  but  the  pans  should  be  suspended  by  platinum  wire 
instead  of  a  silken  cord  as  at  present.  The  top  of  the  box 
forms  the  base  for  the  pans,  which  are  raised  by  a  lever.  These 
balances,  compactly  arranged  in  portable  boxes,  cost,  with  weights, 
from  $26  to  $32. 

Tralles  Balance. — This  is  an  appropriate  apparatus  for  weigh- 
ing heavy  or  bulky  articles,  of  which  the  required  quantities  are 
large,  for  example,  gold  ores,  vegetable  matters,  &c.,  intended 
for  analysis  and  investigation ;  as  in  such  instances,  the  dusty 
emanations  would  render  the  use  of  the  finer  mint  balance  inju- 
dicious. They  are  made  of  sufficient  delicacy  to  turn  with  one  or 
two  grains  when  loaded  with  five  pounds,  and  at  a  cost  of  only 
$20  to  $25. 

The  annexed  drawing  represents  the  instrument,  which  consists 
of  two  brass  dishes  A  A,  suspended  by  loops  D  D,  resting  upon 
the  steel  knife-edges  at  the  extremities  of -the  beam  C.  The 
beam  is  supported  by  the  knife-edge  in  its  centre  as  at  E,  and 
the  whole  balance  is  suspended  to  an  upright,  crooked  at  its  top, 
by  the  hanger  B.  Annexed  to  the  eentre  of  the  beam  is  a  long 
vertical  needle,  which,  following  the  vibrations  of  the  beam, 
serves  to  indicate  the  least  oscillation,  which  is  rendered  more 
perceptible  by  an  ivory  segment  situated  behind  its  point,  and 
divided  into  degrees.  This  balance  is  placed  in  the  room  D,  PL 

8 


114 


PLATFOKM    BALANCE. 


2,  upon  the  table  adjoining  that  upon  which  is  the  finer  balance. 
The  support  to  which  it  is  suspended  may  be  either  of  wood  or 
metal.  To  prevent  damage  to  the  knife-edges,  the  dishes,  when 


Fig.  76  a. 


-A. 


the  scales  are  not  in  use,  should  be  unhung,  and  the  whole  ba- 
lance kept  covered  with  a  linen  cover,  distended  over  a  wire 
framework,  which  may  be  suspended  by  a  cord  upon  a  pulley, 
and  counterpoised  so  as  to  admit  of  being  readily  raised  or 
lowered.  It  would  add  to  the  durability  of  the  balance  to  gild 
the  knife-edges. 

Platform  Balance. — This  is  for  the  general  purposes  of  the 
store-room.     The  best  form  is  that  known  as  "Beranger's  Pen- 
Fig.  77. 


dulum  Scale,"  Fig.  77,  as  it  combines  the  advantages  of  precision, 
strength,  and  durability. 


PRESERVATION  OF  THE  BALANCES.          115 

Preservation  of  the  Balances. — Each  of  the  finer  balances 
should  have  a  separate  table,  and  these  tables  a  permanent  posi- 
tion in  a  close,  well-lighted  room,  expressly  appropriated  for  the 
purpose.  The  top  of  the  table  must  be  of  hard  wood  and  per- 
fectly horizontal;  and  to  secure  the  table  itself  against  the 
slightest  jarring  motion,  it  may  be  tightly  fastened  to  the  floor 
by  iron  clamps  and  screws  fitted  to  its  legs.  Great  care  is  requi- 
site to  have  it  plumb.  Of  the  two  drawers  which  it  should  con- 
tain, one  is  for  the  spatulas,  spoons,  crucible  tongs,  papers,  watch- 
glasses,  and  other  implements  used  in  weighing;  the  other  may 
be  fitted  deskwise,  and  furnished  with  slips  of  paper,  or  a  porce- 
lain slate  and  pencil,  to  afford  convenience  in  recording  the 
weights.  A  polished  cast  iron  slab,  about  six  inches  square,  upon 
which  to  set  the  heated  crucibles  and  promote  their  cooling  by 
conducting  off  the  excess  of  heat  previous  to  weighing,  may  be 
considered  a  necessary  accompaniment  x)f  the  table.  In  order  to 
preserve  its  brightness,  it  should  be  encased  in  a  woollen  bag  and 
kept  within  the  drawer  when  not  in  use  ;  or  it  may  be  enclosed  in 
a  frame  with  a  sliding  cover,  and  fastened  to  the  top  of  the  table 
near  to  one  of  its  corners.  The  cover  which  protects  its  surface 
from  oxidation  can  readily  be  drawn  out  whenever  it  is  required 
to  use  the  slab. 

It  is  not  sufficient  for  the  preservation  of  the  delicacy  of  the 
balances,  that  the  room  in  which  they  are  kept  should  be  dry  and 
tight.  Vapors,  aqueous  and  corrosive,  will  in  divers  ways  find 
entrance  into  the  apartment,  and  so,  therefore,  besides  the  pre- 
caution of  lacquering  the  brass  and  gilding  the  steel  parts  of  the 
balance,  the  instrument  should  be  enclosed  in  a  sufficiently  capa- 
cious mahogany  or  walnut  case,  with  sash-doors  in  the  front  and 
back,  and  sash-windows  at  either  side.  The  doors  should  be 
always  kept  closed  and  fastened  by  their  buttons  when  the  ba- 
lance is  not  in  use,  else  the  entrance  of  dust  and  moisture  will 
impair  its  accuracy.  An  additional  and  very  effectual  precaution 
against  oxidation  by  moisture,  is  to  keep  constantly  within  the 
case  a  glass  containing  some  absorbent  matter,  as  fused  chloride 
of  calcium  or  carbonate  of  potassa.  By  an  occasional  renewal  of 
the  absorbent  matter,  the  atmosphere  within  the  case  can  be 
kept  very  dry.  The  multiplication  of  doorways  is  to  afford  faci- 
lity for  the  passage  and  weighing  of  long  tubes,  which  have  to 


116  THE  BALANCE — THE  WEIGHTS. 

be  placed  across  the'  pan.  The  divisions  in  the  drawer  at  the 
bottom  of  the  ease  must  be  lined  with  velvet,  and  so  arranged  as 
to  receive  the  different  parts  of  the  balance,  and  allow  its  trans- 
portation without  the  least  risk  of  damage. 

In  order  to  preserve  the  edges  of  the  knives,  the  beam  should 
always  be  thrown  out  of  action  when  the  balance  is  not  in  use, 
otherwise  their  constant  contact  with  the  planes,  and  the  pressure 
of  the  balances,  as  well  as  the  sudden  addition  of  a  heavy  weight, 
will  injure  their  delicacy. 

The  three  or  four  feet  upon  which  the  case  rests  have  screws 
passing  through  them.  These  serve  to  give  the  balance  a  per- 
fectly horizontal  position,  even  upon  an  uneven  surface — the 
level  being  obtained  by  raising  or  depressing  either  of  the  screws, 
as  the  case  requires,  and  as  will  be  indicated  by  the  two  spirit- 
levels,  which  should  be  fitted  to  the  pedestal  of  each  balance. 

The.  position  of  the  balance  should  be  with  due  regard  to  light, 
but  while  placed  near  the  window,  to  afford  facility  in  perceiving 
the  slightest  oscillations  of  the  needle,  it  should  be  free  from 
draughts  of  air,  and  also  from  the  action  of  the  solar  rays,  which, 
by  producing  unequal  expansion  of  the  different  parts,  would  occa- 
sion inexact  results  in  weighing. 

The  balances  should  be  cleansed  and  adjusted  whenever  they 
have  become  inaccurate,  for  it  is  almost  impossible  for  even  the 
best  balance  to  retain  its  sensitiveness  indefinitely.  This  work 
should  rather  be  confided  to  a  manufacturer  of  balances,  as  it 
requires  both  skill  and  experience.  Slight  discrepancies  in  the 
weight  of  the  two  dishes  can  be  temporarily  compensated  for  by 
adding  to  that  dish  which  is  deficient,  sufficient  weight  to  restore 
its  equilibrium. 


CHAPTER   VI. 

THE  WEIGHTS. 


THERE  are  three  sets  of  weights  requisite,  of  which  one  for 
the  platform  balance  of  the  store-room  should  be  avoirdupois, 
and  range  from  eight  or  more  pounds  downward  to  a  quarter  of 
an  ounce.  These  weights  are  for  the  rougher  operations  of 


THE  WEIGHTS.  117 

weighing,  and  may  be  of  brass  or  of  cast  iron  coated  with  black 
japan  to  protect  them  against  oxidation. 

For  the  larger  balances,  a  finer  and  exact  set  is  necessary. 
They  should  be  made  of  brass,  in  the  form  of  short  cylinders,  /, 
Fig.  80,  with  knobs  at  the  top,  and  range  from  25,000  to  0-1 
grains,  decreasing  by  fives  in  the  series  to  500,  as  follows: 
25,000,  20,000,  15,000,  10,000,  5,000,1,000,  500;  and  from 
that  point  as  follows:  400,  300,  200,  100,  50,  30,  20,  10,  5,  4, 
3,  2,  1,  0-1. 

The  weights  for  the  analytical  or  assay  balances  must  be  of  the 
finest  and  most  precise  workmanship. 

If  they  are  grain  weights,  the  series  should  range  from  5,000 
grains  to  Tuyoth  of  a  grain,  as  follows:  5,000,.  3,000,  2,000, 
1,000,  500,  300,  200,  100,  50,  30,  20,  10,  5,  3,  2,  1,  -1,  -2,  -3, 
•5,  -05,  -03,  -02,  -01,  -005,  -003,  -002.  The  gramme  weights 
range  from  one  centigramme  to  one  milligramme.  The  divisions 
of  the  gramme  (the  standard  unit  of  the  French  weights)  are  the 
decigramme  =  y^th  gramme;  the  centigramme  =  jjo^h  gramme; 
the  milligramme  =  yiraoth  gramme.  Its  multiples  are  the 
decagramme  =  10  ;  the  hectogramme  =  100  ;  the  kilogramme  = 
1000;  and  the  myriagramme  =  10,000  grammes.  The  table 
below  shows  the  relative  value  and  proportions  of  the  French 
decimal  and  troy  and  avoirdupois  weights  : 

Metrical  or  Decimal  Weights. 
Name,  Equiv.  in  grammes.  ^       Equiv.^.avoirdupois 


Ibs.    oz.         grs. 

Milligramme,  -001  '0154 

Centigramme,  -01  -1543 

Decigramme,  •!  1-5434 

Gramme,  !•  15-434 

Decagramme,  10-  154-3402                  OJ     45- 

Hectogramme,  100-  1543-4023                  3£     12-152 

Kilogramme,  or  Kilo,  1000-  15434-0234           2     3£     12-173 

Myriagramme,  10000-  154340-2344         22     Of     12- 

All  of  the  weights  for  the  fine  balance  must  be  adjusted  with 
the  nicest  accuracy,  and  before  being  used  should  be  compared 
with  others  of  attested  correctness.  Of  the  French  weights  those 
from  the  milligramme  to  the  gramme  should  be  of  platinum  ;  and 
so,  also,  of  the  grain  weights,  those  from  the  ten-grain  weight 
downwards  should  be  of  the  same  metal.  Palladium  being  of 


118  THE   WEIGHTS. 

but  half  the  specific  gravity  of  platinum,  and  similar  to  it  in 
other  respects,  is  sometimes  used  for  the  fractional  grain  weights, 
because  of  the  greater  relative  surface  which  it  presents.  They 
are  frequently  made  of  silver,  and  gilded.  Aluminium  being 
very  light  might  also  be  used  for  the  purpose.  The  remaining 
larger  weights,  to  save  expense,  may  be  of  brass,  and,  to  pre- 
serve them  from  Oxidation,  should  either  be  covered  with  a  thin 
coat  of  lacquer,  or,  better,  galvanized  with  gold  or  platinum. 

Each  set  should  contain  duplicates  of  the  10,  2,  and  1  grain 
weights;  triplicates  of  the  '2,  -1,  '02,  -01,  and  quadruplicates  of 
the  *001  grain  weights;  for  in  many  instances,  especially  in  taking 
specific  gravities,  these  additional  weights  are  indispensable. 
Berlin  balances  are  provided  with  "riders"  which  do  away  with 
the  necessity  of  having  weights  less  than  a  centigramme,  or  hun- 
dredth of  a  grain. 

In  order  to  preserve  the  weights  free  from  dust  and  oxidation, 
they  must  be  encased  in  a  close  box  with  hinged  cover  and  fas- 
tenings. The  interior  of  the  box  should  be  divided  into  com- 
partments, lined  with  velvet,  to  prevent  abrasion  of  the  surfaces 
of  the  weights,  each  of  which  must  have  a  separate  division. 
The  edges  of  every  compartment  should  be  marked  in  ink  with 
the  value  of  the  weight  it  contains ;  and  the  weights  themselves 
must  have  their  denominations  stamped  upon  them.  The  series 
must  be  so  accurately  adjusted,  that  the  difference  between  any 
one  of  the  large  weights  and  the  combined  number  of  smaller 
ones,  equal  to  it,  shall  not  be  perceptible  in  a  balance  turning 
with  one-tenth  of  a  milligramme. 

To  test  their  accuracy,  take  any  two  of  them  of  the  same 
denomination,  convey  them,  with  the  fork  or  forceps,  to  the 
balance,  and  place  one  in  each  dish.  If  the  beam  upon  being 
put  in  action  is  in  perfect  equilibrium,  the  weights  are  uniform, 
and  can  serve  as  standards.  Then,  for  further  verification,  place 
both  together  in  one  dish,  and  in  the  opposite  pan  add  enough  of 
smaller  weights  to  equal  that  of  the  two  combined.  If  the 
beam  still  retains  its  equilibrium,  when  put  in  action,  the  weights 
may  be  considered  correct. 

As  frequent  handling  of-  the  weights  with  the  fingers  would 
tarnish  them,  and  otherwise  injure  their  value,  a  small  fork  and  a 
pair  of  forceps  are  necessary  accompaniments  to  each  set  of 


THE  WEIGHTS.  119 

weights.  The  fork,  represented  by  Fig.  78,  made  of  either 
ivory,  horn,  or  wood,  and  being  intended  for 
raising  the  brass  weights,  has  its  notches  at 
either  end  of  different  size,  so  as  equally  to 
accommodate  the  knobs  of  both  the  larger 
and  smaller  weights.  A  small  pair  of  elastic 
forceps,  Fig.  79,  of  brass  or  plated,  or  po- 
lished steel,  with  ivory  points,  serve  for  the 
smaller  platinum  weights,  which,  for  conveni- 
ence of  handling,  should  be  turned  up  at  one 
corner,  as  at  #,  Fig.  80. 

The  box  should  be  closed  after  each  weighing,  and,  to  preserve 
it  from  the  corrosive  vapors  that  may  be  floating  about,  should  be 
kept  in  the  drawer  of  the  balance-table. 

Fig.  80,  represents  a  box  of  weights  and  all  the  necessary  ap- 
purtenances.    The  ribs,  a  a  a, 
fitted  to  the  interior  of  the  top.  Flg-  80" 

by  pressing  against  them  when 
the  box  is  closed,  %eep  the 
weights  in  their  places.  The 
fork  and  forceps  are  shown  in 
place  at  b  b.  The  channel  df, 
kept  always  covered  with  a 
thick  glass  plate,  contains  the 
platinum  weights,  an  extra  quantity  of  the  smaller  of  which  are 
kept  in  the  cavity  e.  When  the  weights  are  in  constant  use  for 
the  day,  they  may  be,  during  that  period,  kept  on  a  small  stand 
under  a  glass  cover  near  the  balance-pan,  as  shown  in  Fig.  75. 
This  will  save  the  inconvenience  and  delay  of  repeated  transfers 
.  to  and  from  the  box  and  balance. 

Small  weights  may  be  made,  by  first  determining  the  weight 
of  a  given  length  of  wire  of  uniform  thickness  throughout,  and 
then  dividing  it  into  perfectly  equal  parts ; — the  number  of  the 
divisions  or  angles  indicates  the  fraction  of  the  original  weight 
which  they  represent  as  a  whole ;  for  instance,  if  the  wire  weighed 
ten  grains,  and  is  divided  into  10  or  20  portions,  each  fraction 
will  represent  a  grain  or  half  grain,  accordingly. 
By  using  wire  of  greater  thickness,  weights  of  aug-  lg' 

mented  value  can,  in  like  manner,  be  made  and     I I  Z\  I I 

adjusted.     This  form,  as  shown  (Fig.  81),  is  that 


120  WEIGHING. 

in   which   all   weights   below   ten    grains    are    now,   generally, 
made. 

Shot,  of  which  there  should  be  a  box  of  the  several  sizes  kept 
in  the  balance  table-drawer,  are  convenient  counterpoises  for 
tubes,  capsules,  crucibles,  watch-glasses,  and  other  receptacles 
for  substances  to  be  weighed. 


CHAPTER  VII. 

WEIGHING. 

THERE  are  certain  preliminaries  to  be  observed  in  all  delicate 
weighing  operations,  of  which  the  most  important  is  to  ascertain 
whether  the  balance  is  in  order,  as  regards  equilibrium  and  free- 
dom of  oscillation.  To  do  this,  each  dish  should  be  loaded  nearly 
to  the  full  extent  of  the  power  of  the  balance.  If,  when  the 
beam  is  put  in  action,  there  is  no  perceptible  variation  in  the 
dishes,  the  equilibrium  is  perfect.  For  further  verification,  there 
should  be  an  exchange  of  loads,  from  one  dish  to  the  other,  and 
the  beam  again  set  in  motion.  The  recovery  of  the  equilibrium, 
after  the  cessation  of  the  vibrations,  indicates  the  correctness  of 
the  balance.  The  need  of  more  than  a  milligramme  for  the  ana- 
lytic balance,  or  of  T^0th  of  a  milligramme  in  the  more  delicate 
balance,  to  restore  a  deficiency  in  either  dish,  should  condemn 
the  instruments  for  quantitative  examinations,  unless  previously 
adjusted.  This  is  done  by  the  addition  of  bits  of  tin-foil  to  that 
dish  which  is  lightest.  When,  however,  the  balance  is  carefully 
used,  and  by  but  one  operator,  it  will  be  only  necessary  to  re- 
assure himself  of  its  equilibrium  in  those  weighings  where  abso- 
lute accuracy  is  all-important.  Be  careful,  however,  in  adjusting, 
as  well  as  in  weighing,  that  the  weights  in  the  pan  do  not  over- 
load the  balance  and  make  it  set,  an  effect  the  more  prompt,  in 
proportion  to  the  greater  accuracy  and  sensibility  of  the  balance. 
The  setting,  which  makes  one  scale  appear  heavier  than  the 
other,  is  a  permanent  depression  of  the  lowest  pan  by  the  slight- 
est impulse  to  the  exactly  horizontal  beam  of  a  surcharged 
balance.  Hence  the  necessity  of  loading  the  balance  within  the 
limit  of  its  maximum  power. 


WEIGHING.  121 

In  all  weighing  operations,  the  counterpoising  of  substances  is 
more  speedily  attained,  and  with  less  injury  to  the  balance,  by 
systematically  following  a  weight,  which  is  removed  from  the 
pan  as  too  heavy,  by  the  next  in  succession,  until  equilibrium  is 
obtained.  Thus,  in  balancing  a  watch-glass,  if  the  20  grain 
weight  drags  the  beam,  replace  it  by  the  15 ;  if  this  is  still  too 
much,  use  the  10  weight ;  and  if  this  is  too  little,  make  up  the 
deficiency  with  the  smaller  weights,  by  adding  them  consecutively, 
and  decreasing  gradually  their  denomination  as  the  counterpoise 
is  approached. 

To  preserve  the  accuracy  of  the  balance,  it  should  be  put  out 
of  action  upon  every  addition,  removal,  or  substitution  of  weights. 
As  a  precaution  against  error,  the  weights  must  always  be  re- 
moved from  the  pan  and  spread  upon  white  paper  to  be  counted ; 
and  to  verify  the  aggregate,  in  putting  them  away,  their  denomi- 
nations should  also  be  compared  with  their  value,  as  marked  upon 
the  vacancies  which  they  occupy  in  the  box  in  which  they  are 
kept.  The  slips  of  paper  and  porcelain  slate,  in  the  table- 
drawer,  serve  to  make  notes  of  their  amount,  which  should  be 
done  before  placing  them  in  the  box. 

A  provision  against  inaccuracy,  from  very  slight  inequality  of 
the  arms  of  the  beam  or  imperfect  equilibrium  from  other  causes, 
is  the  invariable  use  of  the  same  pan  for  the  reception  of  the 
substance  to  be  weighed.  By  this  practice,  notwithstanding  the 
difference  in  the  weights  of  the  two  dishes,  the  ratio  being  kept 
uniform,  the  quantities  will  be  proportionably  augmented  or  de- 
creased, so  that  the  products  of  analyses  can  be  as  accurately 
estimated  as  in  a  perfect  balance.  An  alternate  use  of  the  pans 
for  the  weights  and  the  substance  to  be  weighed,  will,  on  the 
contrary,  lead  to  results  too  high  or  low,  as  the  case  may  be. 
We,  however,  obtain,  in  this  way,  only  the  relative  weight  of  the 
substance,  and  not  its  absolute  weight,  which  requires  a  perfect 
balance. 

Borda  proposes  to  avoid  the  errors  of  inaccurate  balances,  by  * 
first  taking  the  tare  of  the  substance  with  that  or  any  other 
counterpoise,  and  afterwards  substituting,  in  its  stead,  weights 
sufficient  to  restore  the  equilibrium,  which  was  disturbed  by  its 
withdrawal  from  the  dish.  The  sum  of  these  added  weights  re- 
present exactly  that  of  the  substance  being  weighed.  This  mode 


122  WEIGHING   OF   SOLIDS. 

is  termed  double  weighing,  and  affords  very  nice  results  even  in 
balances  with  disproportioned  beams. 

In  weighing  with  the  Berlin,  or  any  balance  having  the  arms 
of  its  beam  graduated  into  decimal  divisions,  all  weights  less  than 
the  tenth  of  a  grain,  or  the  one-hundredth  of  a  gramme,  may  be 
dispensed  with,  as  the  riders,  heretofore  described  at  p.  118,  are 
much  more  convenient,  and  afford  very  prompt  and  accurate  re- 
sults. 

They  are  looped  forks  of  fine  gilt  wire,  Fig.  82,  weighing 

exactly  •!  of  a   grain   for  grain 
Fig<  82>  weights,  and  -01  of  a  gramme  for 

gramme  weights.  As  the  value  of 
its  weight  upon  the  beam  depends 
upon  its  distance  from  the  point  of 
suspension  of  the  latter,  it  must  be  placed  thereon,  and  moved 
along  from  division  to  division  until  the  exact  point  is  attained, 
by  means  of  the  arm  and  knob  mentioned  at  p.  112.  For  example, 
the  weight  of  the  rider  being  one-tenth  of  a  grain,  it  expresses  at 
division  one,  one-hundredth  placed  in  the  pan ;  at  division  two, 
two-hundredths,  and  so  on.  To  obtain  intermediate  values,  the 
decimal  divisions  of  the  arm  must  be  further  subdivided.  In  the 
use  of  gramme  weights,  the  rider  being  exactly  -01  of  a  gramme, 
any  weight,  from  a  centigramme  downwards,  may  be  determined 
in  the  manner  just  mentioned. 

Weighing  of  Solids. — The  balance  being  in  perfect  order  and 
repose,  the  next  step  is  to  counterpoise  the  vessel  in  which  the 
substance,  which  should  in  no  instance  be  placed  upon  the  naked 
dish,  is  to  be  weighed.  Circular  disks  of  highly  glazed  paper 
are  sometimes  used  as  recipients,  but  being  attractive  of  mois- 
ture, are  preferably  replaced  by  a  watch-glass,  or  crucible  of 
platinum  or  of  porcelain.  The  recipient  being  placed  upon  the 
pan,  appropriated  exclusively  for  the  purpose,  is  then  accurately 
counterbalanced  by  shot  or  fragments  of  metal.  In  analyses, 
the  counterpoise  must  be  preserved  for  future  references.  They 
may  be  either  wrapped  in  paper  or  enclosed  in  paper  pill-boxes, 
but  in  either  case  must  be  labelled.  In  delicate  analyses,  to 
avoid  error,  the  tare  of  the  vessel  should  be  estimated  in  weights, 
and  their  amount  immediately  noted  down,  to  be  afterwards  sub- 
tracted from  the  combined  weight  of  it,  and  the  substance 


WEIGHING  OF   SOLIDS.  123 

weighed.  The  tare  of  the  drying  tubes,  or  of  Liebig's  and  other 
apparatus  used  in  organic  analysis  requiring  to  be  weighed,  to 
prevent  mistakes,  should  be  labelled  upon  the  implements  them- 
selves with  which  it  corresponds.  This  done,  the  substance  is 
introduced  into  the  recipient,  if  in  lumps,  by  means  of  a  pair  of 
forceps  with  platinum  points ;  if  in  powder,  with  an  ivory,  horn, 
or  platinum  spoon  or  spatula,  accordingly  as  it  may  be  inert  or 
corrosive.  The  blade  of  the  spatula  should  never  be  of  steel,  as 
it  is  so  liable  to  oxidation.  A  slip  of  very  thick  sheet  platinum, 
one  inch  in  width  and  two  inches  long,  fastened  in  a  wooden  or 
metallic  handle,  is  generally  used.  Its  usefulness  for  this  pur- 
pose may  be  increased  by  alloying  it  with  a  very  minute  portion 
of  silver,  which  increases  its  elasticity  in  an  eminent  degree. 
The  weights  are  added  to  the  opposite  dish,  and  always  after 
throwing  the  beam  out  of  action,  through  the  side-door  of  the 
case,  which  must  be  immediately  closed  after  each  addition.  If, 
when  the  balance  is  lifted  from  its  supports,  by  means  of  the 
thumb-screw  or  lever,  the  index  needle  turns  rapidly  towards  the 
dish  opposite  to  the  weights,  the  balance  must  be  put  in  repose, 
another  weight  added,  and  the  motion  of  the  needle  again  exa- 
mined. This  operation  should  be  repeated  upon  the  addition  of 
each  weight,  however  small.  As  the  pans  approach  equilibrium, 
the  vibrations  of  the  needle  decrease  in  rapidity,  and  a  little  ex- 
perience and  observation  will  enable  the  operator  to  determine 
the  right  point  after  one  or  two  trials.  When  any  given  quan- 
tity of  a  substance  is  to  be  weighed,  the  requisite  weight  should 
be  placed  in  the  dish  first,  and  the  substance,  if  in  powder,  de- 
posited in  the  other  dish  with  a  spoon  or  spatula,  until  an  accu- 
rate counterpoise  is  obtained ;  taking  care,  however,  to  bring  the 
•balance  at  rest  upon  each  addition  of  material,  which  may  be 
made  to  fall  in  very  minute  quantities  from  the  spatula  by  gently 
tapping  against  its  handle  with  the  finger. 

Those  substances  which  are  hygroscopic,  should  be  weighed  in 
a  covered  vessel ;  for  instance,  between  two  -watch-glasses,  Fig. 
83,  or  in  a  small  tube  with  a  ground  stopper,  which  may  be  held 
in  an  upright  position  by  a  loop  of  platinum  wire  slipped  over 
the  suspending  wire  of  the  pan,  or  by  a  cork  and  wire  stand,  as 
shown  by  Fig.  84. 

The  more  delicate  balances  have  for  this  purpose,  for  that  of 


124  WEIGHING  OF   LIQUIDS. 

organic  analysis  and  of  weighing  substances  in  water,  a  supple- 
mentary pan,  with  a  hook  beneath,  for  convenience  of  suspension, 

Fig.  83. 


This  pan,  which  descends  from  the  beam  only  one-half  the  dis- 
tance of  the  other,  is  shown  in  the  chapter  upon  SPECIFIC  GRAVITY. 
After  the  weighing  is  completed,  the  weights,  as  before 
directed,  are  withdrawn  with  forceps,  placed  upon  a  piece  of 
white  paper,  and  their  several  amounts  added  together; — the 
total  gives  the  weight  of  the  substance  in  the  opposite  dish. 

Covered  vessels  are  also  requisite  for  those  corrosive  sub- 
stances, the  exhalations  from  which  would  be  injurious  to  the 
balance,  and  impair  its  accuracy. 

Substances  should  never  be  weighed  whilst  hot,  even  in  closed 
vessels,  otherwise  the  ascending  current  of  air  thus  produced 
draws  after  it  a  current  of  cold  air,  and  not  only  promotes  an 
unequal  expansion  of  one  arm  of  the  beam,  but  also  an  upward 
motion  to  the  pan,  which  will  lead  to  error.  A  crucible,  therefore, 
which  has  been  over  the  lamp  for  the  ignition  of  its  contents, 
should  be  first  cooled  by  standing  upon  the  iron  slab  accompany- 
ing the  balance-table,  otherwise  its  hot  weight,  not  corresponding 
with  its  cold  weight,  would,  in  estimating  the  result,  lead  to  an 
error  in  the  real  weight. 

Weighing  of  Liquids. — The  nature  of  liquids,  especially  their 
temperature  and  volatility,  have  an  important  influence  upon  the 
precision  of  the  results. 

Non-volatile  liquids  may  be  weighed  in  a  counterpoised  cap- 
sule, watch-glass,  flask,  or  tube.  Those  vessels  which  have 
spherical  bottoms  are  supported  in  the  pans  upon  cork  rings, 
which  are  readily  made  by  hollowing  out  a  cork  and 
bevelling  its  upper  edges  interiorly.  If  the  recipient 
is  tall,  it  requires  a  stand  to  maintain  it  in  an  upright 
position.  This  stand,  shown  by  Fig.  84,  is  nothing 
more  than  a  disk  of  cork  6,  with  the  wire-catch  <z, 
fastened  to  it.  An  excellent  substitute  is  a  broad 
cork,  with  a  hole  in  its  centre,  corresponding  with  the 


WEIGHING   OF   LIQUIDS.  125 

size  of  the  tube,  and  bored  smoothly  and  nearly  through  the 
cork  with  the  cork-borer  hereafter  to  be  described.  The  use  of 
the  wire-loop,  before  mentioned,  is  less  safe  and  convenient  for 
suspending  these  vessels. 

The  liquids  are  conveyed  to  the  recipients  in  dropping-tubes 
or  pipettes.  This  mode  allows  their  gradual  addition,  and  in 
small  quantities. 

Any  excess  of  the  liquid,  preventing  a  perfect  adjustment, 
may  be  removed  from  the  recipient  with  an  empty  pipette  in  the 
same  manner  as  it  was  introduced.  With  a  little  precaution  in 
the  management  of  the  pipette,  the  flow  may  be  made  so  gradual 
that  it  can  be  arrested  as  soon  as  the  vessel  has  received  the  re- 
quired quantity.  The  insertion  of  slips  of  bibulous  paper  serves 
to  withdraw  any  slight  excess,  unless  the  liquid  is  corrosive  and 
acts  upon  paper,  in  which  case,  a  glass  rod  must  be  substituted. 
The  insertion  of  this  rod  into  the  liquid,  and  its  subsequent  with- 
drawal, causes  a  loss  thereto  of  the  small  adherent  quantity,  and 
thus  we  have  a  means  of  accurately  weighing  any  required  quan- 
tity of  liquid. 

The  stock  of  pipettes  should  consist  of  several  sizes.  After 
being  used,  they  should  be  carefully  laid  across  a  porcelain  plate, 
there  to  remain  until  the  completion  of  the  weighing,  when  they 
must  be  well  rinsed  out  previous  to  being  returned  to  their  places 
in  the  drawers. 

All  volatile  substances  must  be  weighed  in  the  small,  closely 
stoppered  flasks,  tubes,  sealed  glass  bulbs,  or  other  vessels,  pre- 
viously counterpoised.  To  insure  accurate  results,  care  must  be 
taken  that  the  temperature  does  not  fayor  volatilization.  Fuming 
liquids  should,  if  possible,  be  measured. 

Very  deliquescent  substances,  such  as  are  not  checked  in  their 
liquefying  tendency  by  the  greatest  practicable  dryness  of  the 
balance-case,  and  are  not  alterable  by  water,  should  be  weighed 
in  solution.  First,  pour  into  the  counterpoised  recipient  a  suffi- 
ciency of  water,  and  note  its  weight.  The  increase  of  weight 
given  to  this  water  by  the  addition  of  the  deliquescent  body,  is 
the  actual  weight  of  the  latter,  and  the  solution  can  be  used  in 
the  analysis  instead  of  the  solid.  In  some  instances,  according 
to  the  nature  of  the  substance,  alcohol,  or  other  more  appropriate 
liquid,  may  be  substituted  for  water. 


126 


WEIGHING   OF   GASES. 


Fig.  85. 


Fig.  86. 


Weighing  of  Gases. — In  weighing  gases,  it  is  necessary,  in 
order  to  obtain  nice  results,  to  guard  against  the  least  variations 
of  temperature,  pressure,  and  humidity  of  the  atmosphere.  Gases 
are  readily  estimated  by  means  of  a  very  sensitive  balance, 
though  the  old  plan,  by  measurement  of  volume  in  graduated 
vessels,  is  accurate  and  easily  executed. 

Gases  are  weighed  in  counterpoised  balloons,  which  must  be 
thoroughly  cleaned  and  dried,  and  wiped  exteriorly  and  interiorly, 
so  as  to  remove  every  particle  of  grease,  dirt,  or  dust.  The  bal- 
loon is  then  to  be  connected  by  a  coupling-cock  fitted  to  its  neck, 
with  an  air-pump  Fig.  47,  or  syringe,  Fig.  86,  and  exhausted  of  its 
air.  To  insure  the  expulsion  of  all  remnants  of  gas  from  a  former 
weighing,  the  balloon  should  be  subjected  to  repeated  alternate 
exhaustions  and  airings.  The  exhausted  balloon  is  then  to  be 
attached  to  a  graduated  bell-glass,  also  fitted  with  a  coupling- 
cock,  as  shown  by  Fig.  85.  This  bell- 
glass  is  the  reservoir  of  the  gas  which  is 
received  or  collected  over  (see  PNEUMATIC 
TROUGH)  water  or  mercury.  Communi- 
cation between  the  balloon  and  bell-glass, 
being  made  by  opening  thein  connecting- 
cocks,  the  gas  rushes  from  the  latter  into 
the  former  by  force  of  atmospheric  pres- 
sure upon  the  mercury.  When  the  bal- 
loon is  filled,  the  flow  is  to  be  stopped  by 
closing  the  cocks.  A  delay  of  several 
minutes  is  necessary  (see  MEASUREMENT 
AND  TRANSFER  OF  GASES)  to  allow  the 
temperature  within  the  bulb  to  become  that  of  the  external  air, 
that  the  level  within  and  without  the  bell-glass  may  be  equalized, 
and  the  quantity  of  gas  noted.  The  balloon  must  then  be  de- 
tached, and  again  weighed  with  care  and  accuracy.  The  diffe- 
rence between  its  present  and  original  weight,  is  that  of  the 
volume  of  gas  which  it  contains. 

In  the  weighing  of  gases,  it  is  indispensable  to  note  the  tem- 
perature and  barometric  pressure,  and  to  observe  all  other  con- 
ditions and  precautions  requisite  in  the  MEASUREMENT  OF  GASES. 
Those  gases  which  are  without  action  upon  mercury,  ought  to 
be  collected  over  that  metal,  for  most  gases,  by  contact  with 
water,  absorb  more  or  less  of  its  vapor,  according  to  the  tempera- 


WEIGHING   OF   GASES. 


127 


ture ;  and,  therefore,  to  insure  correct  results,  it  is  generally 
preferable  to  purify  the  gas  of  moisture  previous  to  weighing  it. 
This  is  done  by  passing  it  through  a  tube  (see  DESICCATION  OF 
GASES)  containing  fused  chloride  of  calcium,  or  some  other  ab- 
sorbent substance. 

It  must  be  remembered,  however,  in  the  desiccation  of  gases,  by 
transit  through  tubes  containing  absorbent  matter,  that  the  quan- 
tity of  dry  gas,  entering  into  the  globe,  is  less  than  that  received 
from  the  bell-glass,  the  volume  of  vapor  abstracted  in  its  passage. 
To  determine  the  amount  of  this  loss,  "  observe  the  temperature 
of  the  moist  gas,  and  correct  its  volume  by  the  pressure  of  thirty 
inches  of  mercury.  Then,  by  the  table  below,  ascertain  the  pro- 
portion of  vapor  which  was  present  in  the  volume  which  left  the 
jar,  and  subtract  it  from  the  corrected  volume ; — the  remainder 
will  be  the  volume  of  dry  gas  whieh  has  entered  the  globe." 

The  table,  taken  from  Faraday,  "  exhibits  the  proportion  by 
volume  of  aqueous  vapor  existing  in  any  gas  standing  over  or  in 
contact  with  water,  at  the  corresponding  temperatures,  and  at 
mean  barometric  pressure  of  thirty  inches." 


40°  — 

•00933 

51°  — 

•01380 

61°  — 

•01923 

71°  — 

•02653 

41  — 

•00973 

52  — 

•01426 

62  — 

•01980 

72  — 

•02740 

42  — 

•01013 

53  — 

•01480 

63  — 

•02000 

73  — 

•02830 

43  — 

•01053 

54  — 

•01533 

64  — 

•02120 

74  — 

•02923 

44  — 

•01093 

55  — 

•01586 

65  — 

•02190 

75  — 

•03020 

45  — 

•01133 

56  — 

•01640 

66  — 

•02260 

76  — 

•03120 

46  — 

•01173 

57  — 

•01693 

67  — 

•02330 

77  — 

•03220 

47  — 

•01213 

58  — 

•01753 

68  — 

•02406 

78  — 

•03323 

48  — 

•01253 

59  — 

•01810 

69  — 

•02483 

79  — 

•03423 

49  — 

•01293 

60  — 

•01866 

70  — 

•02566 

80  — 

•03533 

50  — 

•01333 

* 

This  table  is  also  useful  for  determining  that  part  of  the 
volume  and  weight  of  a  moist  gasy  due  to  aqueous  vapor  after  it 
has  been  weighed  without  previous  desiccation,  for  as  it  "  includes 
any  temperature  at  which  gases  are  likely  to  be  weighed,  the 
proportions  in  bulk  of  vapor  present,  and  consequently  of  the 
dry  gas,  may  easily  be  ascertained.  For  this  purpose  the  ob- 
served temperature  of  the  gas  should  be  looked  for,  and  opposite 
to  it  will  be  found  the  proportion  in  bulk  of  aqueous  vapor  at  a 
pressure  of  30  inches.  The  volume  to  which  this  amounts  should 
be  ascertained  and  corrected  to  mean  temperature.  Then  the 


128  WEIGHING    OF   GASES. 

whole  volume  is  to  be  corrected  to  mean  temperature  and  pres- 
sure, and  the  corrected  volume  of  vapor  subtracted  from  it.  This 
will  leave  the  corrected  volume  of  dry  gas.  It  has  been  ascer- 
tained, in  a  manner  approaching  to  perfect  accuracy,  that  a  cubic 
inch  of  permanent  aqueous  vapor  corrected  to  the  temperature  of 
60°,  and  a  mean  pressure  of  30  inches,  weighs  0-1929  grains. 
The  weight,  therefore,  of  the  known  volume  of  aqueous  vapor  is 
now  easily  ascertained,  and  this  being  subtracted  from  the  weight 
of  the  moist  gas,  will  give  the  weight  of  the  dry  gas,  the  volume 
of  which  is  also  known. 

"  As  an  illustration,  suppose  a  gas  standing  over  water  had 
been  thus  weighed,  and  that  220  cubic  inches  at  the  temperature 
of  50°  Fahr.,  and  barometric  pressure  of  29-4  inches  had  entered 
into  the  globe  and  caused  an  increase  in  weight  of  101-69  grains. 
By  reference  to  the  table  it  will  be  found  that  at  the  temperature 
of  50°,  the  proportion  of  aqueous  vapor  in  gas  standing  over 
water  is  '01333,  which  in  the  220  cubic  inches  will  amount  to 
2*933  cubic  inches,  which,  corrected  to  the  temperature  of  60°, 
becomes  2*942  cubic  inches.  The  whole  volume  corrected  to 
mean  temperature  and  pressure  will  be  found  to  equal  219-929 
cubic  inches,  from  which,  if  the  2*942  cubic  inches  of  aqueous 
vapor  present  be  subtracted,  it  will  leave  216*987  cubic  inches  as 
the  volume  of  dry  gas  at  mean  temperature  and  pressure  :  2-942 
cubic  inches  of  aqueous  vapor  weigh  *5675  grains,  for  2-942x 
0-1929  =  0-5675  ;  this  subtracted  from  101*69,  the  whole  weight, 
leaves  101*1225  grains,  which  is  the  weight  of  the  216-987  cubic 
inches  of  dry  gas ;  and  by  the  simple  rule  of  proportion,  there- 
fore, it  will  be  found  that  100  cubic  inches  of  such  gas,  when 
dried  and  at  mean  temperature  and  pressure,  will  weigh  46*603 
grains. 

"  It  is  not  necessary  in  this  experiment  that  the  globe  or  flask 
be  perfectly  exhausted  of  air  before  the  gas  be  admitted,  all  that 
is  necessary  in  that  respect  being,  that  the  quantity  of  gas  which 
enters,  and  the  corresponding  increase  of  weight,  be  known.  For 
the  same  reason  it  is  not  necessary  that  the  globe  be  filled,  pro- 
vided the  quantity  which  does  enter  is  ascertained  upon  the  gra- 
duation of  the  jar  when  the  level  is  the  same  inside  and  outside ; 
and  that  no  alteration  of  the  quantity  in  the  globe  be  allowed 
before  the  weighing  is  completed.  The  state  and  quantity  of  the 


DETERMINATION   OF    SPECIFIC   GRAVITY.  129 

gas  are  estimated  in  the  jar,  and  it  is  there  that  the  temperature 
and  pressure  should  be  attended  to.  It  is  essentially  necessary 
that  the  temperature  of  the  globe  over  the  water  should  have 
been  steady  for  some  time  before  the  experiment  be  made,  and 
that  it  does  not  change  until  the  gas  has  entered  the  globe  and 
the  stop-cock  is  securely  closed.  After  that,  a  little  variation  of 
temperature  is  of  no  consequence,  so  that  nothing  passes  into  or 
out  of  the  globe  until  the  conclusion  of  the  experiment.  The 
globe,  as  before  said,  should  be  clean  and  dry." 


CHAPTER  VIII. 

THE  DETERMINATION   OF   SPECIFIC   GRAVITY. 

BODIES  which  are  of  uniform  bulk  may  vary  in  density,  and 
thus  give  rise  to  a  difference  in  their  specific  gravity, — the  rela- 
tion of  their  weight  to  their  volume.  The  density  of  bodies  is 
estimated  by  certain  standards ;  that  for  solids  being  pure  dis- 
tilled or  rain  water  (=1-000)  at  62°  F.  The  number,  therefore, 
expressing  the  specific  gravity  of  a  body  is  the  number  of  times 
it  is  heavier  or  lighter  than  an  equal  volume  of  water.  For  ex- 
ample, if  two  bodies  of  equal  bulk  differ  in  density  in  the  ratio  of 
one  to  two,  the  latter  is  said  to  have  twice  the  specific  gravity  of 
the  former,  and  so  in  proportion.  Therefore,  "the  volumes 
being  equal,  the  densities  of  bodies  are  directly  as  their  weights  ; 
or,  the  weights  being  equal,  the  densities  are  inversely  as  their 
volumes." 

"  Thus,  if  a  cubic  centimetre  of  iron  weighs  7'8,  while  an  equal 
volume  of  water  weighs  only  one  gramme,  7'8  is  the  specific  gra- 
vity of  iron."  Hence,  to  find  the  density  or  specific  gravity  of  a 
solid  substance,  its  absolute  weight  must  be  divided  by  the  weight 
of  an  equal  volume  of  water. 

SPECIFIC  GRAVITY  OF  SOLIDS.  By  means  of  the  Balance. — 
The  two  principal  operations  for  estimating  the  specific  gravity 
of  a  solid  heavier  than  water,  are:  first,  to  weigh  it  accurately 
in  air ;  and,  secondly,  to  weigh  it  in  water.  The  weight  at  each 
weighing  must  be  immediately  noted  in  the  record  book. 


130 


SPECIFIC    GRAVITY    OF    SOLIDS. 


All  of  the  finer  balances  are  provided  with  a  supplementary 
pan  (Fig.  87),  for  these  weighings  in  fluids.  Though  necessarily 
but  one-third  the  depth  of  the  regular  pans,  it  is  accurately 
made  so  as  to  exactly  counterbalance  either  of  them,  and  when 
adjusted  to  the  beam,  in  its  stead,  to  maintain  perfect  equilibrium. 
The  hook  beneath  the  pan  is  a  convenience  for  the  suspension  of 
the  body  to  be  weighed.  This  arrangement  permits  the  weighing 
of  the  body  in  air,  and  subsequently  in  water,  without  disturbing 
it  or  the  balance.  The  process  is  as  follows :  Suspend  the  body 
to  be  weighed  by  a  very  fine  platinum  wire  or  unspun  silken 
thread,  to  the  hook  at  the  bottom  of  the  supplementary  pan,  and 
adjust  this  dish  to  that  side  of  the  beam  from  which  the  regular 
dish  has  been  removed  to  give  place  to  it.  There  are  substi- 
tutes for  platinum  and  silk,  but  being  more  permeable  and  less 
capable  of  furnishing  a  very  fine  and  strong  thread,  they  do  not 
aiford  such  nice  results  in  delicate  experiments.  This  done,  take 
the  weight  of  the  body  in  air,  observing  the  requisite  precision  in 
WEIGHING,  and  note  it  down  in  the  record  book  without  delay. 
To  take  the  weight  in  water,  it  is  then  only  necessary  to  convey 
a  beaker-glass  containing  that  liquid  immediately  under  the  dish, 
and  carefully  to  immerse  therein  the  suspended  body.  This  ves- 
sel must  be  of  diameter  sufficient  to  allow  a 
free  play  of  the  body  without  contact  with  its 
sides.  Fig.  87  represents  the  whole  arrange- 
ment. In  introducing  the  body  into  water, 
particularly  if  it  presents  rough  surfaces,  the 
air  attaches  itself  in  bubbles,  which  must  be 
removed  with  either  a  camel's  hair  pencil  or 
wooden  stick.  These  precautions  being  duly 
observed,  put  the  balance  in  action  and  take 
the  weight  of  the  body,  and  immediately  record 
it.  The  apparent  loss  of  weight  represents 
the  weight  of  the  bulk  of  water  which  the  body  displaces,  and 
hence  we  have  the  requisite  data  upon  which  to  calculate  its  spe- 
cific gravity,  viz.,  its  weight  in  air  and  the  weight  of  its  own  bulk 
of  water. 

Thus,  for  example,  the  body  weighs : — 


Fig.  87. 


HYDROSTATIC    BALANCE.  131 

Grains. 

In  air,       .     '..,         .  373 

In  water, 341 

Loss, 32 

By  following  the  rule,  and  dividing  the  total  weight  by  the 
loss  of  weight  in  water,  thus  373—32,  we  have  1-165  as  its  spe- 
cific gravity  or  density. 

If  the  body  is  lighter  than  water,  a  weight  of  known  magni- 
tude and  density  is  joined  with  it  to  sink  it.  The  weight  may 
be  a  capsule,  and  form  a  part  of  the  furniture  of  the  balance  for 
this  especial  purpose.  It  should  be  cullendered  to  allow  the  free 
escape  of  the  globules  of  air  adherent  to  the  body,  after  receiv- 
ing which,  it  should  be  suspended  to  the  short  pan  as  before 
directed. 

In  this,  as  in  the  previous  instance,  the  weight  required  to 
re-establish  the  equilibrium  disturbed  by  the  immersion  of  the 
body  in  water,  expresses  the  weight  of  the  volume  of  water  dis- 
placed. 

"The  rule,  therefore,  is — from  the  difference  between  the 
weight  of  the  two  in  water  and  their  weight  in  air,  subtract  the 
difference  between  the  weight  of  the  heavy  solid  in  air  and  its 
weight  in  water ;  the  remainder  is  the  weight  of  a  quantity  of 
water  equal  in  bulk  to  the  light  solid,  from  which  the  specific 
gravity  of  the  substance  may  be  obtained  by  simple  proportion. 

"As  an  example,  suppose  the  following  case: — 

Grains. 

1.  The  weight  of  the  light  solid  in  air,         .    .      ,       - .,    .   ".      .    .          12 

2.  The  weight  of  the  heavy  solid  in  air,      .....         22 

3.  The  weight  of  the  heavy  solid  in  water,          .         .         .          .          19 

4.  The  weight  of  both  tied  together  in  water,     .....         .         .  8 

Then,  from  the  weight  of  both  in  air  (12-4-22),  .'        ..-        .         .          34 
Deduct  the  weight  of  both  in  water,  .         .    „    .  ,      .         .         .  8 

26 
And  from  the  remainder  deduct  22 — 19=3,         ....  3 

Which  gives  the  weight  of  the  bulk  of  water  displaced  by  the  light 

body  alone,    .  ...         .         .          .         .         .         .         23 

"  The  following  proportion  then  affords  the  specific  gravity  of 
the  body : — 

As  23  :  12  :  :  1-  :  O5217." 


132  STOPPERED    FLASK. 

If  the  substance  is  porous  or  in  powder,  its  specific  gravity  is 
better  estimated  by  weighing  it  in  the  bottle  (Fig.  89),  after  the 
precaution  of  disengaging  all  adherent  globules  of  air ;  other- 
wise it  must,  in  following  the  preceding  process,  be  weighed  in 
a  capsule,  counterpoised  first  in  air  and  afterwards  in  water. 
The  water  also  should,  before  being  used  for  this  purpose,  be 
freed  of  any  contained  air  by  pouring  it  several  times  from  one 
vessel  to  another. 

When  the  body  is  soluble  in  water,  it  must  be  replaced  by  some 
other  liquid  of  determined  specific  gravity,  which  is  without 
action.  Olive  oil,  spirits  of  turpentine,  and  alcohol,  are  appli- 
cable, one  or  the  other,  for  most  cases. 

"  The  specific  gravity  of  the  substance  is  then  found  by  the 
following  proportion :  As  the  density  of  water  is  to  the  density 
of  the  liquid  used,  so  is  the  density  of  the  substance  in  relation 
to  the  liquid  in  which  it  is  weighed  as  unity,  to  its  density  com- 
pared with  water  as  unity." 

"By  the  above-described  process,  we  find  how  much  a  certain 
quantity  of  fluid  weighs  which  has  the  same  volume  with  the  body 
to  be  weighed,  and  when  once  the  specific  gravity  of  the  fluid  is 
known,  it  is  necessary  to  ascertain  the  weight  of  an  equal  volume 
of  water." 

"  Let  it  be  assumed,  that  a  piece  of  salt,  which  is  insoluble  in 
oil  of  turpentine,  weighs  0*352  gram.,  and  displaces  when  put 
into  the  glass  0-13  gram,  of  oil  of  turpentine.  The  specific 
gravity  of  this  fluid  is  0-8725 ; 

0-13 
an  equal  volume  of  water  will  therefore  weigh" =0-149, 

0-8725 

0-352 

and  the  specific  gravity  of  the  salt  is,  therefore, =2-36. 

0*149 

The  preceding  mode  of  taking  the  specific  gravity  of  substances 
is  founded  upon  the  Archimedean  law  of  hydrostatics,  "  that  the 
weight  of  a  substance  in  any  medium  is  less  than  its  absolute 
weight,  by  the  weight  of  the  bulk  of  the  medium  which  it  dis- 
places, obviously  its  own  bulk."  It  is,  however,  not  wholly  un- 
objectionable, as  it  is  liable  to  give  inaccurate  results. 

2d.  By  means  of  a  Stoppered  Flask. — In  this  mode  of  weigh- 


STOPPERED    FLASK.  133 

ing,  which  is  very  available  for  taking  the  density  of  minute  bulks 
of  matter,  and  applies  to  bodies  either  heavier  or  lighter  than 
water,  the  same  attention  to  temperature  is  requisite,  as  in  the 
preceding  process. 

The  glass  bottle,  in  which  the  body  is  to  be  weighed,  is  of  form 
as  shown  by  Figs.  88,  89.  Its  stoppei  should  be  round,  slightly 

conical,  and  accurately  ground.     To  facilitate 

c         :        -  r      Fig.  88.       Fig.  89. 

the  egress  of  any  excess  of  water,  in  case  of 

expansion  by  heat,  and  to  enable  it  to  sink 

to  a  uniform  depth  in  all  positions,  the  centre 

of  the  stopper  should  be  perforated.      The 

precision  with  which  the  bottle  and  its  stopper 

are  manufactured,  'has  an  important  influence 

in  bringing  out  an  exact  result.     This  bottle  is  especially  adapted 

for  taking  the  specific  gravity  of  liquids,  and  its  capacity  may  be 

from  100  to  1000  grains  of  distilled  water. 

Three  weighings  are  required  in  taking  the  specific  gravity  by 
this  mode.  The  flask  is  first  filled  with  water,  so  as  to  exclude 
all  air,  then  conveyed  to  the  balance  and  accurately  counter- 
poised. The  body  to  be  examined  is  then  placed  in  the  same 
pan  with  the  flask,  and  the  balance  being  again  set  in  action,  the 
weight  of  the  body  is  expressed  by  the  additional  weight  neces- 
sary to  produce  equilibrium  ;  and  that  of  the  body  and  flask  by 
the  whole  weight.  The  substance  being  examined,  is  then  placed 
in  the  flask,  which  is  again  weighed,  after  having  been  wiped 
clean,  to  free  it  from  the  displaced  fluid  which  has  flowed  over 
its  sides.  The  third  weighing  is  to  determine  the  quantity  of 
water,  which  is  a  volume  equal  to  its  own  bulk,  displaced  by  the 
immersed  body.  Having  thus  obtained  the  requisite  data,  we 
calculate  as  follows : 


The  glass  vessel  with  water  weighs, 

The  body, 

Both  together, 17-576 

"If,  after  throwing  the  body  into  the  bottle,  putting  the  stop- 
per in,  and  weighing  the  whole  together,  we  find  it  to  be  17*316 


*  * 


AREOMETER. 

grammes,  the  weight  of  the  water  forced  out  by  the  body  must 
be   17*576  — 17'316  —  0-26   gram.;    consequently   the   specific 

4-056 
gravity  of  the  body  is =  15-6." 

3d.  By  means  of  the  Areometer. — The  areometer  is  an  instru- 
ment which  may  be  conveniently  substituted  for  the  balance  in 
taking  the  specific  gravity  of  solids.  That  known  as  Nicholson's 
is  most  generally  used.  Muller  describes  the  apparatus  and  the 
mode  of  manipulating  with  it,  clearly  and  concisely,  as  follows : 
"  To  a  hollow  glass  or  metal  body  A,  Fig.  90,  a  small  heavy 
mass  B  (a  glass  or  metal  sphere  filled  with 
lead)  is  suspended,  and  superiorly  there  is 
attached  to  it  a  fine  stem  supporting  a  plate 
c,  on  which  small  bodies  and  weights  may  be 
laid.  The  instrument  floats  vertically  in  the 
water,  because  its  centre  of  gravity  is  very 
low  in  consequence  of  the  weight  B.  The 
instrument  is  so  arranged  that  the  upper  part 
of  the  body  A  projects  above  the  water.  If 
now  we  lay  the  body,  whose  specific  gravity 
we  would  ascertain,  upon  the  plate  c,  the 
instrument  will  descend,  and  by  adding  ad- 
ditional weight,  we  may  easily  make  it  sink 
to  the  point/,  marked  generally  by  a  line  on 
the  rod.  We  remove  the  mineral  or  other 
substance  we  have  been  using,  and  substitute 
in  its  place  as  many  weights  as  will  again 
make  the  instrument  sink  to  D.  If,  in  the 
place  of  the  mineral,  we  have  had  to  lay  on  n  grains,  the  weight 
of  the  mineral  is  equal  to  n  grains. 

"  If,  in  this  manner,  we  have  ascertained  the  absolute  weight 
of  the  mineral,  the  n  grains  must  be  again  removed,  and  the  body 
laid  in  a  basket  placed  between  A  and  B.  The  instrument  would 
now  again  sink  to  D  if  the  body  laid  in  the  basket  had  not  lost 
weight  by  being  immersed  in  the  water :  we  must,  therefore,  lay 
on  the  plate  the  weight  m  grains,  that  the  body  may  be  immersed 
to  the  mark.  In  this  manner  we  obtain  the  absolute  weight  of 


ALEXANDER  S    METHOD. 


135 


the  body  n,  and  the  weight  of  an  equal  volume 
of  water  m ;  the  specific  gravity  we  seek  is, 

therefore,—  . 
m 

"  If,  for  instance,  we  have  to  determine  the 
specific  gravity  of  a  diamond,  we  must  lay  it 
on  the  plate  and  add  sufficient  weight  to  make 
the  whole  sink  to  D.  If  we  find,  after  remov- 
ing the  diamond,  that  we  must  lay  on  1*2 
grains  to  cause  the  areometer  to  sink  again 
to  the  same  point,  the  absolute  weight  of  the 
stone  would  be  1'2  grains.  These  weights 
must  be  again  taken  away  and  the  diamond 
laid  in  the  basket;  then,  in  order  to  make 
the  instrument  sink  to  D,  we  must  add  0*34 
grains  more;  the  weight  of  a  volume  of  water 
equal  in  volume  to  the  diamond  is,  therefore 
0-34  grains,  and  the  specific  gravity  required 

1-2 


Fig.  91. 


IS 


0-34 


=  3-53." 


4th.  By  Alexander  s  Method. — Analogous 
to  the  method  by  the  bottle  (p.  133),  but  ap- 
plied inversely,  is  the  mode  proposed  and 
employed  by  J.  H.  Alexander,  wherein  the 
precision  attainable  from  the  former  by  minute 
weighings  is  compensated  by  the  largeness  of 
the  masses  that  can  be  operated  with,  and  the 
resulting  accuracy  that,  other  things  being 
equal,  is  always  proportionate  to  the  masses 
employed. 

For  this  an  ordinary  bolt-head  of  glass,  as 
shown  in  Fig.  91,  is  taken,  and  the  weight  of 
its  contents  of  distilled  water  at  a  fixed  tem- 
perature, filled  to  some  convenient  mark  along 
the  stem,  to  serve  as  a  zero-point,  is  carefully 
ascertained.  It  is  most  convenient  for  use  that  this  point  should 
be  adjusted  so  as  to  give  the  weigh  fin  question  at  a  round  num- 


136  ALEXANDER'S  METHOD. 

her  of  grains,  say  10,000 ;  but  in  the  abstract  this  is  quite  imma- 
terial, and  practically  only  serves  to  diminish  the  calculations. 
Then  the  stem  is  divided  by  equal  additions  of  mercury,  in  the 
ordinary  manner,  into  tenths,  hundredths,  and  thousandths  of  the 
capacity  of  the  bulb  and  stem,  below  zero.  The  ten-thousandths, 
which  in  ordinary  cases  will  be  between  BJ0  and  TJ0  of  an  inch, 
are  too  confusing  to  be  engraved  upon  the  stem,  but  can  be 
readily  estimated  by  the  eye,  or  ascertained  more  precisely  by  a 
paper  or  ivory  scale  of  equal  parts. 

To  use  this  implement,  the  specimen  whose  specific  weight  is 
required  is  first  reduced  to  masses  of  a  size  that  will  admit  of 
passing  freely  through  the  stem,  arid  the  actual  weight  of  the 
masses  determined  as  usual.  The  bolt-head  is  then  filled  with 
water  of  a  known  temperature  to  any  stand,  and  in  general  as 
near  zero  and  above  it  as  convenient,  and  the  stand  noted.  Then 
the  weighed  masses  are  introduced  through  the  stem,  and  the 
stand  of  the  water  again  noted.  It  is  manifest  that  the  difference 
between  the  two  stands  is  the  aggregate  volume  of  the  masses 
expressed  by  the  volume  of  water  they  have  displaced,  and  the 
weight  of  these  masses  being  already  known  we  have  both  the 
elements  whose  relation  determines  the  sp.  gr.  sought;  or,  in 
other  words,  we  have  the  absolute  weights  of  water  and  of  the 
substance  in  question,  both  under  the  same  volumes,  and  it  is 
only  necessary  to  divide  the  former  by  the  latter  to  have  the 
specific  gravity  sought. 

Thus,  to  take  an  instance,  let  the  aggregate  weight  of  sundry 
masses  of  bituminous  coal  be  1512*5  grains ;  the  stand  of  the 
water  in  the  stem  before  their  immersion  be  1-0005  and  after 
immersion  1-2115.  The  difference  of  these  readings,  viz.,  1-2115 
—  1-0005  =  0-2110,  multiplied  by  whatever  number  represents 
the  absolute  weight  of  the  unitary  volume  of  water  at  zero,  ex- 
presses the  weight  of  a  volume  of  water  equal  to  that  of  the  coals 
immersed ;  and  in  this  instance  as  the  unitary  weight  is  10,000 
gr.  we  have,  by  merely  removing  the  decimal  point,  this  weight 
as  2110  gr.  Then,  this  weight  divided  by  the  absolute  weight  of 

the  coals,  or  =  1-39504,  the  specific  gravity  sought. 

151.2*5 

Of  course,  this  method  requires  the  same  corrections  to  be  ap- 


ALEXANDER'S  METHOD.  137 

plied  for  the  expansion  of  water  as  do  all  other  methods,  when 
the  temperature  of  the  experiment  varies  materially  from  that  at 
which  the  scale  of  the  instrument  was  originally  adjusted.  Such 
correction  here  can  be  the  most  conveniently  applied  by  using 
respectively,  according  to  the  appropriate  temperature,  the  fac- 
tors in  the  third  column  of  the  following  table  as  multipliers  of 
the  sp.  gr.  obtained.  In  this  table,  the  second  column  gives  the 
absolute  sp.  gr.  of  water,  at  various  temperatures  above  that  of 
maximum  density,  and  is  universally  applicable  in  all  cases  of 
correction  for  temperature.  The  third  column  contains  that  sp. 
gr.  corrected  on  purpose  for  the  expansion  of  the  glass  bulb. 


Temp. 

40° 

Absolute  Weight  of 
Identical  Volumes  of  Water. 

.      .      r— 

Weight  of  Ide 
Volume  of  Walei 

.  ,        .          .           I'— 

45° 

0-99997 

:.•-;    *-T^       .            I'— 

50° 
55° 

0-99986 
0-999G6         .  .      f  •      f- 

';•;#'  .•••*!  i   •      1'— 

09999 

60° 

0-99937 

0-9997 

65° 

H'\   :  .         0-99899 

0-9994 

70° 

;*•,••:'.        0-99853         .m^lllfe 

?»»j»!  W*  ••   .         0-9990 

75° 

80° 

i        .         0-99797         .        . 
O99733         .         .         wf 

0-9985 
=  S    -,    .         .         0-9979 

85° 

0-99660 

0-9972 

Thus,  in  the  example  just  seen,  where  the  unitary  weight  of 
the  water  had  been  adjusted  at  40°  F.,  if  the  observation  had 
been  made  at  a  temp,  of  70°  F.  the  sp.  gr.  first  found  would 
have  been  compared  with  a  fluid  lighter  by  TQOI)  than  water  at 
its  max.  density,  and  the  corrected  sp.  gr.  should  be  1 -39504 X 
0-9990  =  1-39364  to  compare  the  coal  with  water  at  40°  F. 

Of  course,  if  an  instrument  of  this  kind  should  be  adjusted  to 
a  unitary  weight  of  water  at  some  other  temp.,  say  60°  F.,  re- 
gard must  be  had  in  correcting  to  the  proportion  of  the  factors 
above  and  below  such  temperature  and  to  the  consequent  differ- 
ence of  sign.  For  all  cases  above,  the  correction  diminishes  the 
result  at  first  found ;  for  all  cases  below,  it  increases  that  result. 

In  general,  on  the  Continent  of  Europe,  specific  gravities  are 
habitually  referred  to  the  temperature  of  water  at  its  maximum 
density,  rarely  to  that  of  melting  ice,  or  32°  Fahr.  But  in 
England,  the  temperature  of  62°  Fahr.,  which  is  also  the  stand- 
ard of  their  national  weights  and  measures,  is  usually  adopted ; 
as  a  more  practical  point,  and  as  one  which,  more  frequently 


138         SPECIFIC    GRAVITY    OF    BODIES    SOLUBLE    IN    WATER. 

occurring  naturally,  and  more  easily  maintained  artificially,  tends 
to  diminish  the  necessity  for  tabulated  or  special  reductions.  It 
is  to  be  observed,  however,  that  reductions  under  this  system, 
when  they  have  to  be  applied,  are  more  complicated  and  more 
liable  to  errors  of  incaution.  In  America,  the  practice  is  not 
uniform  and  cannot  be  said  to  be  settled,  further  than  in  the 
adoption  by  the  Government  of  the  temperature  of  maximum 
density  for  our  national  standards.  This  adoption,  coupled  with 
what  has  been  already  observed  upon  the  English  system,  and 
with  the  manifest  advantages  of  referring  wherever  we  can  to  a 
natural  zero,  seems  to  justify  the  scale  which  has  been  taken  in 
the  preceding  table,  and  to  warrant  the  uniform  reduction  to  the 
temperature  of  maximum  density. 

No  account  is  here  taken  of  the  expansion,  and  consequent 
diminution  of  density,  which  the  body  itself  operated  on  under- 
goes by  an  augmentation  of  temperature;  both  because  in  general 
the  rate  of  such  expansion  is  unknown  at  the  time,  and  because 
it  would  be,  unless  the  material  be  in  very  large  quantities,  nearly 
inappreciable. 

Specific  Gravity  of  Bodies  Soluble  in  Water. — Besides  this 
method,  whose  results  are  perfectly  accurate,  if  the  liquid  em- 
ployed is  entirely  without  solvent  action  on  the  body  immersed 
(as  it  may  be  either  1°,  because  of  natural  affinities,  or  2°,  because 
of  its  being  previously  saturated  with  molecules  of  the  body  in 
question),  other  modes  have  been  devised  and  practised,  as  by 
Say,  Leslie,  and  Regnault,  whereby  atmospheric  air  is  substituted, 
and  all  contact  with  any  possibly  solvent  liquid  is  avoided.  The 
problem  upon  which  these  last  modes  rest  is  the  measurement  of 
the  same  volume  either  at  constant  or  different  temperatures,  at 
different  pressures ;  a  problem  -whose  performance  is  quite  prac- 
ticable. It  is  manifest  further,  that  such  measurement  can  be 
made  irrespective  of  the  capacity  of  the  vessel  employed,  or, 
what  is  the  same,  just  as  well  when  said  vessel  is  empty  of  all 
but  air,  as  when  it  contains  some  solid  body  besides.  If,  then, 
such  measurement  be  made  first,  and  once  for  all  when  the  vessel 
is  empty,  and  then  again  at  two  different  pressures  when  it  con^ 
tains  the  substance  in  question,  the  expansion  at  the  lower  pres- 
sure being  altogether  that  of  the  air  contained,  and  being  less  in 


. 

SPECIFIC    GRAVITY    OF    FLUIDS.  139 

amount  than  that  of  the  higher,  because  the  volume  of  air  is  less 
by  the  aggregate  volume  of  the  substance  in  question,  the  dif- 
ference between  the  two  volumes  reciprocally,  indicated  by  the 
two  lower  pressures  respectively,  must  be  the  volume  of  the  sub- 
stance in  question ;  the  ratio  of  which  volume  to  its  ascertained 
weight  is  the  specific  gravity. 

Such  is  the  general  principle  of  these  modes,  which  are  entirely 
correct  in  theory,  and  furnish  results  of  an  accuracy  proportfoned 
to  that  of  the  apparatus  and  care  in  manipulation.  Also,  after 
the  apparatus  has  been  once  accurately  tared,  their  application 
requires  less  time  than  the  former  methods,  which,  in  fact,  is  equi- 
valent to  taking  two  specific  gravities, — one  of  the  liquid  in  con- 
tact, the  other  of  the  substance  immersed.  But,  on  the  other 
hand,  these  modes  require,  either  directly  or  indirectly,  a  simul- 
taneous reading  of  the  barometer,  and  also  corrections  for  tempe- 
rature, in  order  to  realize  their  full  precision ;  which  has  formed 
hitherto  an  obstacle  to  the  general  introduction  of  any  of  them 
into  ordinary  laboratories. 

SPECIFIC  GRAVITY  OF  FLUIDS. — There  are  three  modes  of  de- 
termining the  specific  gravity  of  fluids,  which  take  precedence  in 
the  following  order,  viz. :  by  the  stoppered  flask,  the  gravimeter, 
and  hydrometer.  The  first  method  yields  the  greatest  accuracy, 
and  is  that  used  in  all  nice  investigations. 

By  the  Flask. — Any  small  ground  stoppered  flask  or  vial  will 
answer  for  the  purpose.  It  must  first  be  brought  to  the  tempe- 
rature of  60°  F.,  then  accurately  weighed,  and  after  the  removal 
of  the  stopper,  filled  with  distilled  water  of  corresponding  tempe- 
rature. The  stopper  is  then  to  be  inserted,  and  the  water  that 
it  displaces  wiped  from  the  sides  of  the  vessel,  which  when  dry  is 
again  carefully  weighed.  Its  increase  of  weight  expresses  that 
of  the  bulk  of  water  which  it  contains,  and  to  save  time  and 
trouble,  should  be  marked  with  a  diamond  upon  the  neck  of  the 
flask  to  serve  for  future  experiments. 

Glass  flasks  of  this  description  are  made  by  the  manufacturers 
especially  for  this  purpose.  Their  capacities  are  arranged  so  as 
to  exactly  receive  a  given  quantity  of  distilled  water  expressible 
by  weight  in  round  numbers.  The  sizes  vary  from  100  to  1000 
grs.,  but  in  each  instance  they  have  a  diamond  scratch  on  their 


140 


SPECIFIC    GRAVITY    OF    FLUIDS. 


Fig.  92. 


necks  showing  the  measure  of  their  contained  weight  of  water. 
They  have  been  previously  described  at  p.  133,  and  are  repre- 
sented by  Figs.  88,  89.  The  smaller  one  is 
most  used  because  of  greater  facility  in  hand- 
ling. Moreover  the  quantities  of  fluid  under 
examination  are  generally  limited,  and  hence 
the  convenience  of  a  small  flask,  both  on  this 
account,  and  because  it  is  more  easily  weighed 
in  a  delicate  balance. 

For  the  more  volatile  liquids,  and  those  emit- 
ting corrosive  vapors,  the  bottle  should  be 
constructed  as  shown  by  Fig.  92.  A  ther- 
mometer is  adjusted  to  the  mouth,  and  forms 
the  stopper*,  and  there  is  an  upright,  lateral 
tube,  with  an  accurately-fitting  cap.  The  first 
enables  the  operator  to  take  the  temperature 
at  the  moment  of  the  experiment,  and  the 
latter  allows  room  for  expansion  of  the  liquid 
without  risk  of  loss  by  overrunning  or  evapo- 
ration. 

If  the  chemist  prefers  purchasing  a  flask  to 
graduating  one  himself,  it  must  be  verified  as 
above  before  being  used,  and  if  the  weight  of 
its  contents  of  water  does  not  correspond  with 
the  mark  on  the  neck  of  the  flask,  or  of  the 
flask  and  water  combined  with  that  of  the 
weight  generally  accompanying  it  as  a  con- 
venient counterpoise,  then  the  flask  is  not  to 
be  relied  on,  and  should  either  be  corrected  or  rejected. 

In  either  case  the  flask  must  be  thoroughly  cleansed,  and  after 
each  experiment  should  be  repeatedly  rinsed  with  distilled  water, 
so  that  it  may  be  perfectly  clean  and  dry  when  wanted  for  the 
next  operation.  In  emergencies,  the  interior  may  be  dried  by 
placing  the  flask  upon  the  sand-bath ;  in  this  case,  however,  it 
will  be  necessary  to  allow  its  temperature  to  fall  again  to  62° 
before  using  it. 

Distilled  water  at  62°  F..is  the  standard  by  which  to  estimate 
the  specific  gravity  of  liquids.  To  take  the  density  of  a  liquid, 


HYDROMETERS.  141 

equal  bulks  of  it  and  water  are  taken  at  the  balance.  The  flask 
having  been  graduated,  its  weight  and  that  of  the  bulk  of  its  con- 
tents of  water  are  already  known  ;  it  is,  therefore,  only  necessary 
to  fill  it  with  the  liquid  under  examination  at  62°  F.,  to  the  mark 
upon  its  neck,  and  after  inserting  the  stopper,  carefully  weigh  it. 
Divide  the  weight  thus  found  by  the  weight  of  the  water  (as  in- 
dicated on  the  flask)  and  you  obtain  the  specific  gravity  of  the 
liquid.  For  example  : — 

Grains. 

The  clean  and  dry  flask  weighs 400 

Do.  do.          filled  with  pure  water,  at  62°       .         .          .         900 

Deduct  the  first  from  the  latter  and  you  obtain  the  weight  of 
the  water  —  500.  Supposing,  then,  that  the  same  bulk  of  the 
liquid  weighs  412  grains,  then  412  4-  500  =  0-824,  its  specific 
gravity. 

If  the  capacity  of  the  flask  is  1000  grains  of  water,  and  one 
of  that  size,  may  well  be  used,  when  the  stock  of  the  liquid 
under  examination  is  not  limited,  the  process  is  still  easier.  It 
is  then  only  necessary  to  fill  it  with  the  fluid  and  weigh  it. 
The  weight  obtained  expresses  its  specific  gravity ;  thus,  taking 
mercury  for  example,  a  bulk  of  that  metal  equal  to  the  bulk  of 
1000  grains  of  water,  is  13,500  grains,  and,  therefore,  these 
latter  numbers  express  its  density,  jcare  being  observed  to  advance 
the  decimal  point  three  figures  to  the  left,  if  the  water  is  taken 
as  1  instead  of  1-000. 

The  vessel  must,  previous  to  weighing,  be  invariably  wiped 
dry  exteriorly  with  a  linen  cloth,  and  to  avoid  any  communica- 
tion of  heat  from  the  hands,  they  should  be  gloved. 

For  determining  the  density  of  very  minute  quantities  of  rare 
liquids,  it  will  be  necessary  to  have  the  aforementioned  bottles  of 
miniature  dimension,  or  else  to  replace  them  by  glass  bulbs. 

If  the  fluid  is  volatile  and  readily  vaporizable,  it  should,  in 
being  raised  to  the  proper  temperature,  be  heated  over  a  spirit 
lamp,  in  a  test  tube ;  taking  care  to  keep  the  finger  over  its 
mouth,  during  the  heating  and  cooling,  so  as  to  prevent  its  being 
unclosed. 

By  the  0-ravimeter. — The  density  of  fluids,  whether  heavier 


142  GRAVIMETERS. 

or  lighter  than  water,  may  be  very  conveniently  and  precisely 
ascertained  by  the  hydrostatic  balance  or  any  delicate  beam,  one 
of  whose  arms  is  furnished  with  a  metallic  ball  of 
Fig.  93.  known  weight,  and  so  connected  as  to  be  plunged 
into  the  fluid  in  question.  (See  Fig.  93.)  In  the 
laboratory  of  this  University,  this  ball  is  pear- 
shaped,  of  brass,  heavily  gilt  to  prevent  any  che- 
mical action  of  the  liquid  upon  it,  and  attached 
by  the  finest  platinum  wire,  the  weight  of  which, 
per  inch,  is  also  ascertained.  It  is  manifest 
that  the  absolute  weight  and  the  volume  of  any 
body  being  constant,  the  apparent  diminution  of 
weight  it  sustains,  upon  being  immersed  in  any  fluid,  becomes 
less,  i.  e.,  the  counterpoise  required  becomes  greater,  just  as  the 
density  of  the  circumambient  fluid  diminishes ;  and  that  in  coun- 
terpoising such  a  body,  the  ball,  for  instance,  just  spoken  of,  im- 
mersed successively  in  fluids  of  different  densities,  we  are  obtain- 
ing the  weights  of  identical  volumes  of  the  fluids  respectively, 
and  if  one  of  those  fluids  be  water,  the  technical  specific  gravities 
of  all  the  others. 

The  application  of  these  principles,  and  the  convenience  of  the 
method  itself,  will  be  better  seen  by  an  actual  numerical  example 
of  determining  the  specific  gravity  of  sperm  oil.  In  this,  the 
temperature  at  the  beginning  and  end  of  the  observations  was 
constant  at  64-5°  F. ;  the  barometer  stand  29-95  inches,  so  little 
differing  from  the  standard  as  not  to  be  worth  noting  for  correc- 
tion. The  counterpoise  to  the  ball  in  air  was  172-60  grains ;  in 
water,  118-70  grains;  in  the  oil,  125-19  grains.  The  respective 
differences  between  the  first  and  the  last  two,  viz.,  53-90  grains 
and  47-41  grains,  give  at  once  the  ratio  of  the  specific  gravity  of 
the  water  to  that  of  the  oil,  as  1  :  0-87959,  which,  if  the  circum- 
tances  in  the  cases  of  the  two  fluids  were  the  same,  would  be 
the  final  result.  In  point  of  fact,  however,  the  circumstances 
were  not  the  same ;  for  the  immersion  of  the  platinum  wire, 
which  weighed  0-047  grains  per  inch,  was  in  the  water  0-5  inch, 
and  in  the  oil  0-3  inch ;  leaving  0-2  inch  of  wire,  corresponding 
to  0-0094  grains  in  absolute  weight,  less  in  the  oil  than  in  the 
water.  This  surplus  weight,  of  course,  had  to  be  borne  by  the 
counterpoise,  which  it  increased  by  its  own  amount ;  leaving  out 


GRAVIMETERF.  143 

of  the  view  the  remote  correction  for  the  different  displacement 
by  the  constant  mass  of  the  platinum  of  varying  volumes  of  water 
and  oil.  It  is,  therefore,  to  be  subtracted  from  the  oil  counter- 
poise, or,  what  is  the  same,  added  at  once  to  the  47*41  grains 
loss  of  weight  in  oil ;  making  47'4194  grains  to  be  divided  by 
53-9  grains,  the  loss  in  water,  and  resulting  in  a  quotient  of 
0-87977,  the  specific  gravity  of  oil  at  64-5°  F.,  that  of  water,  at 
the  same  temperature,  being  considered  unity. 

But  water  is  systematically  unity  only  at  its  maximum  density, 
say  40°  F.,  and  oil  increases  in  density  0-000423  for  every  de- 
gree downward,  at  least  to  that  temperature,  and  probably  still 
lower,  until  near  its  freezing-point.  If,  therefore,  oil  be  taken 
for  unity  at  40°  F.,  its  proportionate  density  at  64'5°  F.  will  be 
1  _  (0-000423  X  64-5°  —  40°)  =  0-98964.  That  of  water  at 
64-5°  F.,  may  be  ascertained  with  sufficient  precision  from  the 
table  just  now  given,  by  taking  proportional  parts  between  the 
temperatures  and  densities  there  given.  Thus,  the  difference 
between  60°  and  65°  is  5°,  of  which  the  difference  between  65° 
and  64-5°  is  the  tenth  part ;  also,  the  difference  between  the  spe- 
cific gravity  corresponding,  or  0-99937  and  0-99899  is  0-00038, 
of  which  the  proportional  tenth  part  is  0-000038,  or,  say  0-00004 
to  be  added  to  0-99899,  making  the  density  of  water  at  64-5°  = 
0-99903.  The  final  density  of  oil,  then,  at  40°  F.,  will  be  to  the 
density  at  64*5°  F.,  in  the  inverse  ratio  of  these  proportionate 
numbers;  or  fffgf  •  0-87977  =  0-88812,  the  ultimate  specific 
gravity  of  oil  compared  with  water  as  !•,  both  being  at  the  tem- 
perature of  40°  F.  Such  is  the  mode  of  applying  the  reductions 
in  question,  which  belong  universally  to  all  methods  of  determin- 
ing specific  gravities. 

By  Nicholson  s  Areometer. — "  The  specific  gravity  of  liquids 
may  also  be  determined  by  Nicholson's  areometer,  Fig.  90.  As 
the  instrument  always  sinks  so  far  that  its  weight,  added  to  the 
weight  upon  the  plate,  is  equal  to  the  mass  of  liquid  displaced, 
we  may,  by  the  aid  of  this  instrument,  ascertain  how  much  a 
definite  volume  of  water  weighs.  It  is  necessary,  however,  to 
know  the  weight  of  the  instrument  itself.  Suppose  this  weight 
to  be  n,  we  must  lay  on  some  additional  weight  to  make  the  in- 
strument sink  to  D ;  if  we  designate  this  addition  by  a,  then  is 
n  +  a  the  weight  of  water  displaced. 


144  HYDROMETERS. 

"  If  we  immerse  the  instrument  in  another  liquid,  we  must  lay 
on  another  weight  b  in  the  place  of  a,  to  make  the  whole  sink  to 
D ;  b  will  be  greater  than  a  if  the  liquid  be  denser,  and  less  than 
a  if  it  be  lighter  than  water.  The  weight  of  the  liquid  displaced 
is  n  +  b ;  but  its  volume  is  exactly  as  great  as  the  volume  of  the 
mass  of  water,  whose  weight  is  n  -f  a,  because  the  areometer  has 
sunk  equally  deep  in  both  cases. 

"  Suppose  the  instrument  weigh  70  grains,  we  must  add  20 
grains  to  make  it  sink  in  water,  and  1-37,  that  it  may  sink  to  the 
point  /  in  spirits  of  wine ;  then  the  specific  gravity  of  spirits  of 

.      .     70  -f  1-37       n  7QO  „ 

wme  M  7ir+^o =  °'793- 

By  the  Hydrometer. — Hydrometers  do  not  give  very  accurate 
results,  but  they  are  convenient  when  time  is  an  object,  and  no 
great  precision  is  requisite.  Their  action  is  based  upon  the 
hydrostatic  law,  "  that  a  floating  body  displaces  its  own  weight 
of  the  liquid  in  which  it  swims.'1 

The  instrument  consists  of  a  glass  stem  A,  with  an  air-bulb, 
B,  beneath,  properly  ballasted  with  mercury  or  shot,  I).  The 
depth  to  which  the  hydrometer  will  sink  in  a  liquid  is  proportioned 
to  its  rarity,  for  the  denser  the  liquid,  the  less  of  it  will  be  displaced. 
A  properly  graduated  scale  inserted  within  the  stem  or  spindle, 
Fig.  94.  Fig.  95.  allows  the  appreciation  of  the  density  of  a 
liquid  by  the  greater  or  less  depth  to  which 
it  sinks  therein.  The  form  of  this  instrument 
is  shown  by  Figs.  94,  95.  They  are  con- 
structed with  different  scales,  according  as 
they  are  intended  for  liquids  rarer  or  denser 
than  water.  The  scales  for  those  which  are 
rare  run  from  zero  (at  the  bottom  of  the 
stem)  upwards.  The  graduation  of  the  scale 
for  liquids  denser  than  water  is  reversed. 

Areometers   are   variously  graduated   for 
different  liquids,  thus — 

Those  for  ether  mark  upwards  from  10  to  50° 

"       "    spirits     "  u     10  to  SO 

C«J»1,  *    gait*       *     downwards"       0  to  40 

-*.       u    acids      **      ?>.*•>-    •-*•       Oto75 
*        "    syrups    tf  "  "       0  to  36 


HYDROMETERS. 


145 


The  following  table  shows  the  specific  gravity  numbers  corre- 
sponding with  Baume's  areometric  degrees : — 


LIQUIDS  DENSEH  THAN  WATER. 

LESS  DENSE  THAN  WATER. 

09 

«0 

. 

. 

4 

, 

, 

«c  ~" 

i       *j 

«.-*j 

« 

«=  Z? 

s 

U-  Z? 

« 

§J? 

1 

II 

bo 

i 

£  rt 

WO 

1 

I] 

tBO 

£ 

Q 

n 

OJO 

bio 

Q 

Is 

0 

1  -0000 

26 

1-2063 

52 

•5200 

10 

1  -0000 

36 

0-8488 

1 

1-0066 

27 

1-2160 

53 

•5353 

''41 

0-9932 

37 

0-8439 

2 

1-0133 

28 

1-2258 

54 

•5510 

12 

0-9865 

38 

0-8391 

3 

1-0201 

29 

1-2358 

55 

•5671 

13 

0-9799 

39 

0  8343 

4 

1-0270 

30 

1-2459 

56 

•5833 

14 

0  9733 

40 

0-8295 

5 

1-0340 

31 

1-2562 

57 

•6000 

15 

0-9669 

41 

0-8249 

6 

1-0411 

32 

1-2667 

58 

•6170 

16 

0-9605 

42 

0-8202 

7 

1-0483 

33 

1-2773 

59 

•6344 

17 

0-9542 

43 

0-8156 

8 

1-0556 

34 

1-2881 

60 

•6522 

18 

0-9480 

44 

0-8111 

9- 

1-0630 

35 

1-2992 

61 

•6705 

19 

0-9420 

45 

0-8066 

10 

1-0704 

36 

1-3103 

62 

•6889 

20 

0-9359 

46 

0-8022 

11 

1-0780 

37 

1-3217 

63 

•7079 

21 

0-9300 

47 

0-7978 

12 

•0857 

38 

1-3333 

64 

•7273 

22 

0-9241 

48 

0-7935 

13 

•0935 

39 

1-3451 

65 

•7471 

23 

0-9183 

49 

0-7892 

14 

•1014 

40 

1-3571 

66 

•7674 

24 

0-9125 

50 

0-7840 

15 

•1095 

41 

1-3694 

67 

•7882 

25 

0  9068 

51 

0-7807 

16 

•1176 

42 

1-3818 

~fe8~" 

1-8095 

26 

0-9012 

52 

0-7766 

17 

•1259 

43 

1-3945 

69 

1-8313 

27 

0-8957 

53 

0-7725 

18 

•1343 

44 

1-4074 

70 

1-8537 

28 

0-8902 

54 

0-7684 

19 

1-1428 

45 

1-4206 

71 

1-8765 

29* 

0-S848 

55 

0-7643 

20 

1-1515 

46 

1-4339 

72 

1-9000 

30 

0-8795 

56 

0-7604 

21 

1-1603 

47 

1-4476 

73 

1-9241 

31 

08742 

57 

0-7356 

22 

1-1692 

48 

1-4615 

74 

1-9487 

32 

0-8690 

58 

0-7526 

23 

1-1783 

49 

1-4758 

75 

1-9740 

33 

0-8639 

59 

0-7487 

24 

1-1875 

50 

1-4902 

76 

2-0000 

34 

0-8588 

60 

0-7449 

25 

1-1968 

51 

1-4951 

35 

0-8538 

61 

0-7411 

The  hydrometer  is  used  with  a  tall  glass  jar  (Fig. 
96),  which  serves  as  a  recipient  for  the  liquid  to  be 
tested.  After  having  perfectly  cleansed  it  of  grease 
and  dirt  with  a  cloth,  it  is  to  be  placed  in  the  jar,  and 
the  liquor,  first  brought  to  62°  F.,  added.  When  it 
becomes  stationary,  note  the  degree  at  which  it  stands. 
For  verification,  raise  it  an  inch  or  more  out  of  the 
liquid,  and  then  let  it  gradually  sink  back  again.  If 
it  reaches  the  same  point  as  before,  the  first  observa- 
tion was  correct.  In  reading  the  divisions  on  the 
scale,  do  not  take  that  line  where  the  liquid  rises  in 
wetting  the  stem  of  the  instrument,  but  note  it  at  the 

10 


Fig.  96. 


146 


HYDROMETERS. 


Fig.  97. 


real  level,  which  is  the  curvature  pro- 
duced by  the  ascending  motion  of  the 
liquid  against  the  sides  of  the  spindle. 

Hydrometers  graduated  by  Baumk's 
process  are  generally  used. 

By  Ham's  Method. — This  requires 
the  use  of  a  special  apparatus,  by  means 
of  which  the  air  is  made  to  take  the 
place  of  the  balance.  It  is  said  to  yield 
accurate  results  with  great  promptness. 
It  consists  of  two  glass  tubes,  A  and  B, 
Fig.  97,  20  to  24  inches  long,  and  with 
bores  of  one-fourth  to  three-eighths  of 
an  inch  diameter.  A  semicircular  brass 
tube  and  cock  C  connect  them  at  the 
top ;  and  their  lower  ends,  which  are 
left  open,  dip  into  two  glass  vessels  or 
beakers  D  E,  one  of  which  is  to  contain 
distilled  water,  and  the  other  the  liquid 
under  examination.  These  latter  are 
supported  by  stands  kept  in  adjustment 
by  the  milled-headed  screws  F  G,  and 
the  bracket  and  nuts  H.  The  scale  I  I 
is  divided  into  two  hundred  parts.  By 
increasing  the  number  of  divisions  or 
degrees  to  2000  the  instrument  may  be 
rendered  still  more  exact. 

Distilled  water  being  poured  into  one 
of  the  beakers,  and  the  liquid  to  be 
tested  in  the  other,  air  is  to  be  drawn 
from  the  tubes  by  attaching  a  syringe 
to  the  cock  C,  until  the  lightest  fluid  is 
nearly  at  the  top  of  one  of  the  tubes. 
The  surfaces  of  the  two  fluids  in  the 
vessels  D  and  E  are  then  equalized,  or 
brought  to  a  a  by  raising  or  depressing 
the  stands  by  means  of  the  screws,  as 
may  be  required.  The  heights  of  the 
fluids  in  their  respective  tubes  will  im- 


SPECIFIC   GRAVITY   OF   GASES. 


147 


mediately  show  their  relative  densities,  convertible  into  water  at 
1000  by  simple  proportion. 

The  liquids  should  be  at  60°  F.,  or  some  uniform  tempera- 
ture approximating  that  point,  at  the  time  of  the  experiment. 

SPECIFIC  GRAVITY  OF  GASES. — The  extreme  lightness  of  gases 
and  vapors  renders  it  inconvenient  to  compare  their  weight  with 
that  of  an  equal  bulk  of  water,  and  consequently  air  is  taken  as 
the  standard. 

The  mode  of  taking  these  specific  gravities  is  thus  concisely 
and  clearly  described  by  Parnell:  "  From  the  careful  experiments 
of  Dr.  Prout,  it  appears  that  100  cubic  inches  of  atmospheric  air 
deprived  of  carbonic  acid  and  aqueous  vapor  weigh  31-0117 
grains,  at  30  inches  of  the  barometer,  and  at  the  temperature 
of  60°  F. ;  from  which  observation  it  is  easy  to  calculate  the  abso- 
lute weight  of  any  bulk  of  a  gas  from  its  specific  gravity.  Thus 
the  specific  gravity  of  chlorine  is  found  to  be  2*47 ;  to  find  how 
much  100  cubic  inches  of  that  gas  weigh  at  mean  temperature 
and  pressure,  we  make  use  of  the  proportion, 

As  1  :2-47::  3T01  :  76-59; 

therefore  100  cubic  inches  of  chlorine  weigh  76'59  grains. 

The  simplest  method  of  obtaining  the  specific  gravity  of  a 
gas  is  the  following : — The  object  is  to  ascertain  the  weight  of  a 
bulk  of  gas  equal  to  the  bulk  of  a  known  weight  of  air.  For  this 
purpose,  a  light  glass  globe,  furnished  with  a  stop- 
cock, is  very  accurately  weighed,  when  full  of  air; 
then  exhausted  of  its  air,  by  connecting  it  with  an 
air-pump,  and  weighed  in  the  vacuous  state.  The 
weight  of  the  air  withdrawn  by  the  exhaustion  is 
thus  ascertained.  The  globe,  still  vacuous,  is  con- 
nected with  a  jar  containing  the  gas  (Fig.  98) 
which  is  to  be  weighed,  at  the  water  or  mercurial 
trough ;  the  jar  having  a  stop-cock  at  its  top, 
into  which  the  stop-cock  of  the  globe  can  be 
screwed  air-tight.  On  gently  opening  both  stop- 
cocks, a  quantity  of  gas  rushes  from  the  jar  into 
the  exhausted  globe,  equal  in  bulk  to  the  air  with- 
drawn by  the  exhaustion,  if  the  surface  of  the  liquid 
within  the  jar  be  brought  to  the  level  of  that  without  in  the 


Fig.  98. 


148  SPECIFIC    GRAVITY    OF    GASES. 

trough,  and  the  temperature  of  the  air  and  the  barometric  pres- 
sure have  not  varied  during  the  experiment.  The  stop-cock  being 
closed,  the  globe  is  detached  from  the  jar,  and  weighed.  The 
difference  between  its  weight  when  containing  the  gas,  and  when 
vacuous,  is  the  weight  of  a  bulk  of  the  gas  equal  to  the  bulk 
of  air  whose  place  it  occupies,  the  weight  of  which  has  already 
been  determined. 

Suppose  the  globe  to  lose  10-33  grains  by  exhaustion  of  air, 
and,  when  exhausted,  to  gain  15*78  grains  by  admitting  carbonic 
acid  gas ;  then,  assuming  1*  as  the  density  of  air,  we  have  the 
proportion, 

As  10-33  :  15-78  ::  1  :  1-527; 

the  specific  gravity  of  carbonic  acid  gas  is,  therefore,  1'527. 

Although  thus  simple  in  principle,  the  operation  in  its  de- 
tails is  one  of  extreme  delicacy.  From  the  facility  with  which 
gases  undergo  a  change  in  their  bulk  through  variations  of  tem- 
perature and  pressure,  it  is  obvious  that  if  the  temperature  and 
barometric  pressure  vary  during  the  course  of  the  experiment, 
corrections  must  be  made.  As  an  illustration  of  the  necessary 
corrections,  suppose  the  bulk  of  air  to  weigh  12  grains  at  the 
temperature  of  60°  F.,  and  under  a  pressure  of  30  inches  bar. ; 
and  the  same  bulk  of  the  gas  whose  density  is  required  to  weigh 
20  grains,  but  at  the  temperature  of  50°  F.,  and  under  a  pressure 
of  28  inches  bar.  The  points  to  be  determined  here  are  two : — 

1.  Considering  the  volume  of  the  air  withdrawn  and  the  gas 
admitted  as  !•,  at  the  observed  temperatures  and  pressures,  what 
would  be  the  volume  of  the  gas  at  the  temperature  and  pressure 
at  which  the  air  was  weighed  ? 

And,  2,  having  obtained  that  volume,  what  is  the  corre- 
sponding increase  or  reduction  in  the  weight  of  the  gas  ? 

Performed  according  to  rules  which  are  given  in  the  note 
below,*  the  results  of  these  calculations  are  as  follows  : — 

*  "  1.  For  Changes  in  Bulk  by  Pressure. — The  volume  which  a  gas  should  pos- 
sess at  one  pressure  may  be  calculated  from  its  known  volume  at  another  pressure, 
by  the  use  of  the  following  proportion : — As  the  pressure  to  which  the  gas  is  to  be 
corrected  is  to  the  observed  pressure,  so  is  the  observed  volume  to  the  volume  re- 
quired. In  the  example  in  the  -text  (6),  the  pressure  to  which  the  gas  is  to  be 
reduced  is  30  inches,  the  observed  pressure  28  inches,  and  the  volume  is  1-019. 
Then,  as  30  :  28 :  :  1-019  :  0-951. 

U2.  For  Changes  in  Bulk  by  Temperature. — From  the  very  recent  experiments 


SPECIFIC   GRAVITY  OF   GASES.  149 

(a)  A  volume  of  gas  equal  to  !•  at  50°  F.  is  equal  to  1'019 

at  60°  F. 

(b)  A  volume  of  gas  equal  to  1*019  at  28  inches  of  the  baro- 

meter is  equal  to  0-951  at  thirty  inches. 
A  volume  of  the  gas,  therefore,  requal  to  0-951  weighs  20 
grains  ;  a  volume  of  air  equal  to  !•  at  the  same  temperature  and 
pressure  weighing  12  grains.     Then,  if  0-951  vol.  weighs  20 
grains,  1  vol.  should  weigh  21-03  grains  ;  and 

As  12  :  1  ::  21-03:  V75; 

1-75  is,  therefore,  the  density  required. 

The  state  of  dryness  of  a  gas  is  another  circumstance  which 
interferes  with  its  volume  ;  for  which  reason,  due  care  should  be 
taken  to  insure  either  the  perfect  dryness  of  the  gas,  or  its  com- 
plete saturation  with  moisture.  In  the  latter  case,  the  tempera- 
ture must  be  noticed,  and  the  observed  volume  reduced  according 
to  the  proportion  of  aqueous  vapor  capable  of  existing  in  the  gas 
at  the  observed  temperature.  The  proportions  of  vapor  by  vo- 
lume contained  in  one  vol.  of  the  saturated  gas  for  temperatures 
between  40°  and  80°  F.  are  expressed  in  the  table  at  page  127. 
A  cubic  inch  .of  aqueous  vapor  corrected  to  the  temperature  of 
60°,  and  at  a  pressure  of  30  inches,  weighs  0*1929  grains. 

The  preceding  method  of  obtaining  the  density  of  a  gas  still 
requires  a  slight  correction  from  another  circumstance,  when  the 
temperature  and  pressure  differ  considerably  at  the  time  of  weigh- 
ing the  air  and  at  the  time  of  weighing  the  gas  ;  but  one  so  trifling 
that  it  may,  in  general,  be  neglected.  The  necessity  of  this  cor- 

of  M.  Regnault,  it  appears  that  a  volume  of  gas  expands  by  heat  ¥£^  of  its  bulk 
for  each  degree  Fahrenheit.  Hence,  the  volume  of  a  gas  at  0°  F.  being  1,  at  any 

higher  temperature  it  is  found  by  the  formtila  1  -\  --  emp'         .     The  determination 

459 

of  the  volume  of  a  gas  at  one  temperature  from  its  known  volume  at  another  tem- 
perature may  be  attained  by  the  following  formula  :  —  Let  t  be  the  temperature 
Fahrenheit  at  which  the  volume  of  the  gas  is  observed  ;  tr  the  temperature  Fah- 
renheit to  which  the  volume  of  the  gas  is  to  be  reduced;  x  the  observed  volume 
at  t  ;  and  xf  the  volume  at  t'  required  ; 


"3.  It  is  frequently  necessary  to  combine  corrections  both  for  temperature  and 
pressure.  In  such  a  case,  as  in  the  example  in  the  text,  the  reduction  of  volume  is 
first  made  for  temperature,  and  that  corrected  volume  is  afterwards  reduced  ac- 
cording to  the  pressure. 


150  SPECIFIC   GRAVITY   OF   VAPORS. 

rection  arises  from  the  impossibility  of  obtaining  a  perfect  vacuum 
in  the  globe ;  and  the  remaining  small  quantity  of  air  may  oc- 
cupy a  different  space  when  weighed  with  the  gas,  to  that  which 
it  occupied  when  the  globe  was  weighed  with  air ;  and  conse- 
quently the  bulk  of  the  gas  admitted  into  the  globe  is  not  the 
same  as  the  bulk  of  the  air  withdrawn.  If  the  amount  of  rare- 
faction of  the  air  in  the  exhausted  flask  is  observed,  by  means  of 
a  barometer  gauge  attached  to  the  air-pump,  the  amount  of  the 
remaining  air  may  be  calculated  when  the  weight  of  the  quantity 
withdrawn  is  ascertained ;  then  the  alteration  to  which  it  would 
be  subject  in  bulk  by  changes  of  temperature  and  pressure  may 
also  be  estimated,  and  a  due  allowance  made  on  the  bulk  of  the 
gas  admitted  into  the  globe." 

When  the  gas  is  corrosive  in  its  action,  as  in  the  case  of  chlo- 
rine, the  balloon  with  its  metallic  cock  must  be  replaced  by  a 
glass  flask,  with  a  nicely-fitting  ground  stopper.  This  flask  is  to 
be  adjusted  to  a  drying-tube  connected  with  the  vessel  in  which 
the  chlorine  is  generated.  The  bent  end  of  the  drying-tube 
entering  the  flask  should  reach  to  its  bottom.  The  disengaged 
gas,  in  passing  through  the  tube,  parts  with  its  moisture,  and 
reaching  the  flask  descends  to  the  bottom,  and  displaces  the  air, 
which  is  expelled  through  the  interstices  at  the  mouth  around  the 
tube.  When  the  chlorine  itself  begins  to  escape,  it  is  evidence 
that  all  the  air  has  been  displaced,  and  the  flask  is  then  to  be 
slowly  and  gently  detached  from  the  apparatus  and  hermetically 
closed  with  its  ground  stopper. 

Fig.  99. 


SPECIFIC  GRAVITY  OF  VAPORS. — The  following  method,  devised 


SPECIFIC   GRAVITY   OF   VAPORS. 


151 


by  Dumas,  is  applicable  to  all  substances  vaporizing,  without  de- 
composition, at  temperatures  less  than  the  fusing-point  of  hard 
glass. 

Take  a  glass  globe  of  about  12  to  16  oz.  capacity,  with  a  long 
slender  neck,  wash  it  with  distilled  water,  and  carefully  dry  it, 
either  by  slight  warmth  or  by  means  of  the  exhausting  syringe 
and  a  tube  filled  with  chloride  of  calcium.  (Fig.  99.)  After  the 
balloon  is  perfectly  dry,  its  neck  is  to  be  drawn  out  to  a  narrow 
tube,  6  or  8  inches  long,  and  bent  nearly  at  a  right  angle,  as 
shown  at  a,  Fig.  100.  The  tip  is  then  to  be  removed  with  a  file, 

Fig.  100. 


and  the  mouth  of  the  tube  rounded  (not  closed)  over  the  blow- 
pipe flame.  The  globe  full  of  air  is  now  weighed,  with  great 
precision,  and  afterwards  warmed  to  expel  a  portion  of  its  air. 
This  done,  and  the  temperature  and  barometric  pressure  having 
been  observed,  its  beak  is  immediately  dipped  into  the  liquid  or 
melted*  solid  matter,  and  as  the  air  within  contracts  by  the  cool- 
ing of  the  bulb,  which  may  be  hastened  by  dropping  ether  on  its 
exterior,  the  fluid  is  drawn  up.  When  the  requisite  quantity, 
say  100  to  150  grains,  has  entered,  the  globe  is  at  once  enclosed 
in  a  wire  basket  5,  Fig.  100,  and  introduced  into  a  cast  iron  kettle 
containing  water  for  the  bath,  when  the  temperature  is  not  to 

*  If  the  solid  body  is  not  fusible,  a  given  weight  of  it  is  introduced  into  the  globe, 
previously  dried.  The  neck  is  then  drawn  out,  the  end  removed  and  placed  in 
the  balance.  By  deducting  its  weight  from  that  of  the  whole  balloon,  you  obtain 
the  weight  of  the  balloon  full  of  air. 


152  SPECIFIC    GRAVITY   OF   VAPORS. 

exceed  212°  F.  Solution  of  chloride  of  calcium  must  be  used 
for  temperatures  near  250°,  neat's-foot  oil  when  300°  is  required, 
and  metal  baths  for  higher  degrees.  The  wooden  support  e,  to 
an  arm  of  which  is  suspended  the  thermometer  c,  keeps  the  globe 
firmly  fixed  in  the  bath. 

The  bath  is  brought  to  ebullition,  and  as  soon  as  it  rises  above 
the  boiling-point  of  the  substance,  a  jet  of  vapor  escapes  through 
the  tube,  and  as  soon  as  it  ceases,  the  point  is  quickly  sealed  up 
over  the  blow-pipe  flame,  observing  at  the  same  time  the  tem- 
perature of  the  bath  and  the  barometric  pressure. 

The  globe  thus  closed  is  then  withdrawn  from  the  bath,  washed, 
dried,  and  again  weighed. 

To  determine  the  capacity  of  the  balloon,  its  tube  is  dipped 
into  mercury,  and  its  point  broken  under  the  surface  of  the 
metal,  which  immediately  rushes  in  and  fills  the  vacuum  caused 
by  the  condensation  of  the  vapor,  and  should  occupy  the  whole 
interior.  It  is  evident  that  the  volume  of  mercury  represents 
the  volume  of  the  vapor  at  the  noted  temperature,  and  this 
volume  is  determined  by  transferring  the  mercury  to  a  graduated 
tube,  and  marking  the  number  of  cubic  inches  or  centimetres 
which  it  occupies. 

We  thus  have  all  the  data  necessary  for  calculating  the  specific 
gravity  of  the  vapor,  having  determined,  experimentally, — 
"  1.  The  weight  of  the  globe  and  air  at  ordinary  temperature 

and  pressure ; 

"  2.  The  weight  of  the  globe  and  vapor  filling  it  at  the  tempera- 
ture of  the  bath,  and  under  ordinary  pressure ;  and, 
"  3.  The  capacity  of  the  globe. 

"  Haying  these  results,  we  obtain  by  calculation, — 
"  1.  The  weight  of  the  empty  globe  (by  knowing  the  capacity  of 

the  globe,  the  weight  of  the  air  filling  it  can  be  calculated, 

which,  deducted  from  the  weight  of  the  globe  and  air,  leaves 

the  weight  of  the  globe  when  vacuous) ; 
"  2.  The  weight  of  vapor  filling  the  globe  at  the  temperature  of 

the  bath  (by  deducting  the  weight  of  the  empty  globe  from  the 

weight  of  the  globe  and  vapor) ;  and, 
"  3.  The  weight  of  air  filling  the  globe  at  the  temperature  of  the 

bath,  and  at  the  pressure  at  which  the  globe  was  sealed*  with 

the  vapor. 


SPECIFIC   GRAVITY  OF  VAPORS.  153 

"  The  last  calculation  is  made  according  to  rules  given  in  the 
note,  pp.  147  and  148 ;  having  performed  which,  the  density  of 
the  vapor  required  is  obtained  by  the  simple  proportion, — As  the 
weight  of  air  filling  the  globe  at  the  temperature  of  the  bath  is  to 
the  weight  of  vapor  filling  the  globe  at  the  same  temperature,  so 
is  1  to  the  density  required." 

It  is  necessary  to  remark,  that  in  the  instances  of  organic  sub- 
stances which  are  sensitive  to  the  decomposing  influence  of  the 
air  at  the  temperature  to  which  their  vapors  must  be  heated,  in 
order  to  obtain  constant  densities,  the  glass  globe  should  be  filled 
with  carbonic  acid  gas  previous  to  heating  the  bath.  The  mani- 
pulations, thereafter,  are  as  already  directed. 

The  following  table  of  the  densities  of  a  large  number  of  sub- 
stances, and  for  which  we  are  indebted  to  Th.  J.  Herapath 
(Chemist,  vol.  4),  will  be  found  very  convenient  for  reference. 
It  comprises  the  most  reliable  results ;  and  in  instances  of  doubt 
or  discrepancy,  conflicting  numbers  are  also  given,  with  a  note  of 
interrogation  affixed  to  the  most  questionable.  The  *  attached  to 
certain  names  is  intended  to  indicate  that  the  authority  cited  is 
not  responsible  for  the  numbers,  as  they  were  merely  quoted  from 
those  writers. 


154 


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TABLE    OF    SPECIFIC    GRAVITIES. 


Authority. 

*d*_ 

Stromeyer. 
Cresy.* 

Thomson. 
Vernon. 
Karsten. 
Macaire  Princep. 

Moselev.* 

1                I 

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Substances. 

Sapphire,  . 
Oriental, 

cT 
co 

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3 

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^       Ji  1 

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Resins,  tacamahac, 
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Rhodochrome,  . 

'o       >» 

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55    £ 

Rochelle-salt, 
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cicc!     ciKcococo     mmmmm     m        mm 

TABLE    OF    SPECIFIC    GRAVITIES. 


183 


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TABLE    OF   SPECIFIC    GRAVITIES.  185 


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TABLE    OF    SPECIFIC    GRAVITIES.  191 


CHEMICAL  TABLES, 

NOTES  on  the  TABLE  of  DENSITIES. 

ACETIC  ACID. — Specific  gravity  is  not  a  certain  criterion  of  the  (Strength  of 
acetic  acid,  when  the  latter  contains  more  than  about  34£  per  cent,  of  water. 
— Mollerat. 

The  acetometer  of  the1  Messrs.  Taylor  has  for  its  basis  the  strength  of 
proof  acid  (Pr.  v.),  called  by  the  manufacturer  No.  24. 

Table,  by  the  Messrs.   Taylor,  showing  the  proportion  of  real  acid  per  cent, 
at  different  densities  :  — 
Pr.  V.— 1-0085,  5<> ;  1'017,  10«  ;  1-0257,  15g  ;  1-032,  20  j  ;  1-047,  30g  ;  1-058,  40g. 

When  acetic  acid  is  converted  into  acetate  of  lime,  the  decimal  fraction  of 
the  density  is  very  near  doubled  ; — thus,  1  009  in  pure  acetic  acid  becomes 
T018  in  acetate  of  lime. — (See  Viriegar.) 

AETHER. — Table,  showing  the  specific  gravity  of  mixtures  of  alcohol  and  ether  ; 

by  Dalton.— Pure  ether,  0'72(?) ;  90+10,  0  732  ;  80+20,  0:744  ;  70+30,  0'756  ; 

60+40,  0-768;  50+50,  0'780  ;   40+60,  0'792 ;  30+70,  0'804  ;   20+80,  0-816; 

1G+RO,  0-826  ;  0+100,  0  83  (Spirit). 

ALCOHOL. — For  tables  of  the  density  of  various  mixtures  of  alcohol  and  water, 

see  "  Brande's  Manual,"  "  Ure's  Dictionary,"  and  other  works. 
ALLOYS. — Alloys  which  possess  a  density  greater  than  the  mean  of  their  consti- 
tuents:— 

Gold  with  antimony,  bismuth,  cobalt,  tin,  or  zinc;  silver  with  antimony, 
bismuth,  lead,  tin, or  zinc  ;  lead  with  antimony  ;  platinum  with  molybdenum  j 
palladium  with  bismuth;  copper  with  bismuth,  palladium,  tin,  or  zinc. 
Alloys  which  possess  a  density  less  than  the  mean  of  their  constituents : — 
Gold  with  copper,  iron,  lead,  iridium,  nickel,  or  silver;  silver  wiih  copper 
or  lead;  iron  with  antimony,  bismuih,  or  lead;  tin  and  antimony,  lead,  or 
palladium,  nickel,  and  arsenic  ;  zinc  and  antimony.—  Thtnard. 
AMMONIA.— See  "  Tables,"  by  Ure,  Dalton,  Davy,  &c. 

"  Ure's  Table,"  is  generally  considered  to  be  the  most  correct. 
BARLEY. — If  not  more  than  five  "pickles"  (or  grains)  per  hundred  float,  when 
unmalted  barley  is  thrown  into  water,  it  is  considered  by  tradesmen  to  be  a 
good  sample  of  grain;  if  more,  the  contrary.  After  malting,  the  grain  be- 
comes specifically  lighter,  and  when  thrown  into  water,  will  float  in  a  longi- 
tudinal position  ;  in  good  malt,  only  about  five  pickles  per  hundred  will  sink  ; 
grain  that  has  been  partially  malted  will  remain  perpendicularly  suspended 
in  the  water. 

BEER. — The  rule  employed  by  Mr.  Warington  for  converting  the  saccharometric 
indication  (by  Richardson's  instrument)  of  the  wort  into  real  specific  gravity, 
is  as  follows: — Divide  the  saccharometer  indication  by  360, and  then  add  one. 
Example — 

36-4-360+1  "CO  =1-1  sp.gr. 

Richardson's  saccharometer  indicates  by  how  many  pounds  a  barrel  of  wort 
of  a  certain  density  is  heavier  than  a  barrel  of  pure  water  (viz.,  360  Ibs.)  To 
convert  saccharometric  indication  into  real  gravity,  add  the  number  indicated 
(say  x)  to  360,  and  make  the  following  simple  calculation  : — 

360  :  360+a:  :    :  ] I  :  true  density. 

The  scale  of  Dicas's  instrument  is  nearly  as  5  to  2  of  Richardson's  ;  i.  e. 
80  by  the  latter  are  about  equal  to  200  by  the  former. 

Allan's  saccharometer  indicates  the  true  specific  gravity. 

BLOOD. — The  density  of  the  blood,  and  of  the  serum  of  the  blood,  is  increased 
in  plethora,  cholera,  &c.,  and  diminished  during  pregnancy,  and  in  pneumo- 
nia, bronchitis,  pleuritis,  tubercular  phthisis,  fever  (?),  and  chlorosis. 
THE  EARTH. — The  density  of  the  earth  is  supposed  to  increase  in  an  arithme- 
tical progression  at  the  rate  of  about  '38  for  every  100  miles,  as  we  penetrate 
through  the  exterior  crust  towards  the  centre. 


102  TABLE    OF    SPECIFIC    GRAVITIES. 

GAS. — A  diffusion  experiment  affords  the  elements  for  calculating  the  specific  gra- 
vity of  a  gas. 

,  A  x  a 
The  specific  gravity  =  ( ~~  j 

Where  G  is  the  measure  of  gas  submitted  to  diffusion,  and  A  the  measure  of 
return  air.— Edinb.  Phil.  Trans.  XII,  222. 

One  hundred  cubic  inches  of  dry  air,  at  29'92  inches  Bar.,  weigh  32'5SS64 
grs.  at  32°  F.,  and  30-82926  grs.  at  60°  Y.—Eegnaull. 

GLASS. — The  density  of  annealed  glass  is  greater  than  that  of  the  unannealed. 
The  phenomena  of  devitrification  are  always  accompanied  by  an  increase  in 
density;  thus,  soda  glass  being  =2-485,  the  devitrified  glass  is=2'503. — 
Spliltgerber. 

HYDROCHLORIC  ACID. —Sue  tables  by  Davy,  Thomson,  Ure,  Kirwan,  and 
Dalton.  Ure's  results  are  considered  the  most  accurate. 

HYDROCYANIC  ACID.— 0'957,  16«  ;  0'9?68,  10'6g;  0'9815,  9'lg;  0'9S4,  8g  ; 
0-987,  7'3»;  0'989,  6'4o  ;  0'99,  5'8»  ;  0'9923,  5'0»  ;  0'994,  4g  ;  0-9958,  3«  ; 
0-9974,  2»  ;  0'9979,  1'6«.— Dr.  Ure. 

MAGNESIA  (SULPHATE  OF).— For  a  table,  by  Anthon,  see  Gmelin's  Hand- 
book (English  trans.) 

NITRIC  ACID. — Tables  by  Ure,  Thomson,  Kirwan,  and  Dalton,  are  contained 
in  most  of  the  manuals.  Ure's  table  appears  to 'be  the  most  correct. 

OILS  (FIXED). — The  zero  of  the  scale  in  the  so-called  Elaeometer  is  placed 
where  the  instrument  would  float  in  pure  oil  of  poppy  seeds;  the  space  be- 
tween this  point  and  that  which  marks  the  density  of  pure  olive  oil  is  gene- 
rally divided  into  50  degrees.  The  density  of  pure  almond  oil  is  about  equal 
to  38  or  38i  degrees  by  this  scale.  The  Oleometer  of  M.  Laurot  is  so  gradu- 
ated as  to  sink  to  zero  in  pure  colza  oil  (heated  to  212°  F.) ;  to  210°  in  rape- 
seed  oil ;  to  124°  in  poppy  oil ;  to  83°  in  fish  oil ;  and  to  136°  in  oil  of  hemp- 
seed. 

PHOSPHORIC  ACID.— Sp.  gr.  1-85,  50<>  anhyd.  acid  :  1-6,  40g  ;  1-39,  30. g  ;  1'23, 
200  ;  1-1,  lOg.— Dalton. 

POTASH.— For  tables  showing  the  proportion  of  caustic  potash,  and  hydrate  of 
potash,  contained  in  lyes  of  different  strength,  see  the  works  of  Ure,  Brande, 
Gmelin,  &,c.  Ure's  table  appears  to  be  the  most  accurate. 

POTASH  (CARBONATE  OF).— For  table,  by  Tiinnermann,  see  works  of 
Brande,  Gmelin,  &c 

POTASH  (CHROMATE  OF).— S.G.  1-28,  50g  ;  1'21,  338  ;  M8,  250  ;  M5,  20|> . 
1-12,  160.;  Ml,  140.;  1-1,  12".— Dr.  Ure. 

PYROXYLIC  SPIRIT For  table,  see  Ure's  Dictionary  of  Arts,  &c. 

ROOT-CROPS. — The  relative  densities  of  different  roots  or  tubers,  are'stated  by 

Mr.  Hyett,  to  be  as  follows: — 
Turnips  : — Pomeranian  globe,  889  ;  Green  round,  905  ;  Border  imperial,  932  ; 

— average,  908-57. 
Swedes:— Purple -topped,    949;    Green-topped,    952;     Skirving's,    972;— 

average,  957  67. 
Mangold-wurzel : — Long-red,  995-25  ;    Red-globe,    1005'7;    Yellow-globe, 

1014-6;— average,  1005-18. 
Potatoes.— Rohan,  1081  to  1089'95 ;   Purples,  1091  to  1102;  Welsh-kidney, 

1 107  to  1 108  ;— average,  1096'49. 

The  specific  gravity  of  small  roots  appears  generally  to  exceed  that  of  large 
roots.  Mr.  Hyett  says,  "  That  the  determination  of  the  densities  of  root- 
crops,  affords  an  easy  though  rough  method  of  estimating  their  relative 
powers  of  nourishment. "(?) 

SODA. — For  tables,  by  Richter  and  Tiinnermann,  of  the  proportion  of  hydrate  of 
soda  and  anhydrous  soda,  contained  in  lyes  of  different  densities,  see  the 
works  of  Gmelin,  Brande,  Ure,  &c. 

The  following  table  is  by  Dalton,  and  shows  the  percentage  of  NaO. 

Sp.  G.  1-85,  63-60;  l-72,53'8g;  1'63,  46'6-g  ;  1 -56,41-20;  1'5,  36'8Q  ;  T47, 
340;  1-44,310;  1-40,  29o;.  1-36,  26g  ;  1'32,  23 {f ;  1'29,  19g  ;  1'23,  160;  M8, 
13«  ;  1-12,  90.;  1-06,4-70. 

SODA  (CARBONATE  OF).— For  table,  see  Gmelin's  Handbook. 
SODA  (NITRATE  OF).— See  Richter's  tables  ;  Stoichiometrie  3'164. 
SODA  (SULPHATE  OF).— See  Brandes  and  Gruner,  Br.  Arch.  22-148. 


TABLE   OP   SPECIFIC   GRAVITIES.  193 

SODIUM  (CHLORIDE  OF).— The  proportions  of  salt  in   solutions  of  different 

densities,  at  62°  FM  is  shown  below. 
S.G.  1-0283,  l-24th;  1'0275,  l-25th ;  1'027,  l-26th  ;  1'0267,  l-27th  ;  1'025, 

l-28th;  1-0233,  l-30th;  1-0185,  l-39th;  1'0133,  l-44th ;  T0105,  l-56th ; 

1-004,  l-108th;  1'0023,  l-162d. 

[Calculated  by  Mr.  Kirwan,  from  Watson's  results.] 

SUGAR. — According  to  Dr.  Ure,  if  the  decimal  part  of  the  number  representing  the 
specific  gravity  of  syrup,  be  multiplied  by  26,  the  product  will  denote  very 
nearly  the  quantity  of  sugar  per  gallon  in  pounds  weight,  at  the  given  sp.  gr. 

Table,  by  Dr.  Ure,  showing  the  percentage  of  sugar,  in  saccharine  solutions 
of  different  densities  :  — 
Sp.  Gr.  1-326,  666660  sugar ;  1-231,  5Qo  ;  M777,  400  ;  M44,  33'333<>  ;  M34, 

31-25°;  1-125,  29-412«;  Mil    26'316o  ;  MC45,  25g;  1'0905,>  21'74g  ;  l'C82, 

20g  .  1-0635,  16-6660  ;  1-Q5,  12-5$  ;  1-0395,  10g. 
For  more  extensive  tables,  see  the  different  chemical  manuals  ;  also,  Evan's, 

Porter's,  and  Dutrone's  works  on  the  Sugar  Manufacture. 
At  1-342,  syrup  of  the  cane  contains  70$  of  sugar  ;  at  the  same  density  syrup 

of  starch  sugar  contains  75^  per  cent. —  Vre. 

For  a  table  of  the  densities  of  alcoholic  solutions  of  sugar,  see  Ure's  Diction- 
ary of  Arts,  Manufactures,  &c. 

SULPHURIC  ACID.— For  tables,  by  Parkes,  Ure,  Bineau,  &c.,  see  Ure's  Dic- 
tionary,   Grnelin's    Handbook,    Parnell's    Applied    Chemistry,    and    other 
manuals. 
Bineau's  table  is  said  to  be  the  most  correct,  but  as  the  results  are  calculated 

to  32°  F.,  Ure's  table  is  the  one  most  commonly  accepted. 

URINE.— To  determine  the  proportion  of  solid  matters  in  urine,  multiply  the  differ- 
ence between  the  density  of  the  urine  and  that  of  water  by  2'58  (Dr.  Henry), 
or  by  2'33  (according  to  Christison),the  product  shows  the  quantity  of  solid 
matters  in  1000  grs.  of  urine.  Thus,  giving  a  urine  of  T004  sp.  gr. :  1004 — 
1000=4,  which,  multiplied  by  2'58,  gives  10'32  as  the  weight  in  grains  of 
solids  in  1000  grs.  of  urine.  According  to  Becquerel,  the  proportion  of  sugar 
in  a  specimen  of  diabetic  urine  may  be  ascertained  by  using  the  factor  1'65  as 
above.  Millon  says,  that  "  the  second  and  third  figures  after  the  point  (in  the 
density)  express  with  tolerable  exactness  the  quantity  of  urea  in  1000  parts  of 
the  urine.  Thus,  urine  of  T011  contains  about  11  parts  in  1000  of  urea.  In 
the  urine  of  animals  and  pathological  urines,  however,  M.  Millon  admits  that 
this  correspondence  is  no  longer  observed.  The  density  of  the  urine  is  gene- 
rally below  the  normal  standard  in  Diabetes  insipidus(\'QQ3  to  1*005 — Percy), 
hysteria,  Bright's  disease  (?),  chlorosis,  and  jaundice  (?);  and  above,  in  Dia- 
betes mellitus  (1"032  to  1'048),  erysipelas,  fever,  bronchitis,  haemoptysis,  and 
other  inflammatory  diseases.  It  is  generally  higher  in  the  afternoon  (1 '023  to 
1-028)  than  in  the  forenoon  (1'017  to  1*022),  evening  (1'019  to  1'028),  or  night, 
(1-012  to  1-025.) 

VINEGAR. — Vinegar  of  malt,  of  a  density  of  1'014,  becomes  only  1  '023  when  con- 
verted into  acetate  of  lime  ;  "005  of  its  density  is  due  to  mucilaginous  matter. 
—  Ure. 

WATER. — The  temperature  at  which  pure  water  attains  its  greatest  density,  ao- 
cording  to  different  observers,  is  as  follows  : — 

38°  F.,  Dalton;  38'75°,  Stampfer ;  38'8°,  Eumford ;  38'804°,  Munch; 
39o,  Sir  C.  Blagden—Gilpin;  39' 101°,  Playfair  andVowZe;  39'176°,  Despretz; 
39-38,  Hiillstrom  ;  39'5,  Hope  :  40°,  Lefebvre  Gineau  ;  41°,  Deluc. 

Despretz's  determination  is  generally  believed  to  be  the  most  correct. 

Sea-water  (from  the  Southern  Ocean),  according  to  Bladh,  attains  its 
maximum  density  at  36*59°  F. 

WOODS. — The  densities  given  in  the  table  have  reference  to  the  dry  and  well- 
seasoned  woods,  in  their  natural  condition. 

The  true  specific  gravities  of  these  woods  (i.  e.  when  the  air  in  the  inter- 
stices of  the  wood  has  been  expelled)  are,  according  to  Count  Rumford,  as 
follows : — 

Birch,  1-4848;  beech,  1-5284;  elm,  1'5186;  fir,  1-4621;  lime,  1'4846; 
maple,  1-4599;  oak,  1-5344;  poplar,  1'4854. 

13 


194 


MEASURING   OF   FLUIDS. 


Fig.  101. 


Fig.  102. 


CHAPTER   IX. 

MEASURES  AND   MEASURING. 

Measuring  of  Fluids. — When  great  accuracy  is  required  in 
the  estimation  of  fluids,  their  weight  is  determined;  but  in  ordi- 
nary operations,  the  amount  of  their  volume  is  obtained  by  the 
employment  of  vessels  purposely  prepared  and  graduated  with 
care  and  precision. 

These  vessels,  or  graduates  as  they  are  called,  are  generally 
of  two  forms,  those  for  the  larger  operations  being  cylindrical, 
as  shown  by  Fig.  101.  This  shape  combines  both  strength  and 
convenience.  For  the  smaller  (ounce  or  drachm)  graduates  the 
conical  form,  Fig.  102,  is  preferable,  as  giving  greater  facility,  by 
its  smaller  surfaces,  for  accurately  estimating  minute  volumes. 

Graduation. — For  the  large 
measures,  the  imperial  pint  is 
the  usual  integer.  To  graduate 
a  vessel  to  this  extent,  take  a 
glass  balloon,  counterbalance  it, 
and  weigh  therein  accurately 
one  pint  imperial,  34-659  cubic 
inches  (8750  grs.),  of  distilled 
water,  at  the  temperature  of 
62°  F.,  and  at  30  inches  of  ba- 
rometric pressure.  After  the  vessel  has  remained 
undisturbed  upon  a  level  shelf,  sufficiently  long 
for  its  contents  to  acquire  a  smooth  steady  sur- 
face, scratch  upon  the  neck  the  exact  line  to 
which  the  liquid  rises.  The  narrower  the  neck  of  the  flask  the 
greater  the  facility  in  noting  this  point  without  liability  of  error. 
This  weighed  quantity  of  water  is  then  to  be  transferred  to  the 
proof  glass,  under  process,  of  form  as  shown  in  Fig.  101.  After 
the  water  has  settled,  and  presents  a  smooth  calm  surface,  its 
level  is  to  be  scratched  accurately  upon  the  exterior  of  the 
glass,  either  with  a  diamond-point  or  a  sharp  file.  A  reli- 
able pint  measure  is  thus  obtained,  to  graduate  which  into 
its  subdivisions  of  ounces  and  drachms,  it  is  only  necessary  to 


GRADUATION    OF   VESSELS.  195 

take  the  weights  of  these  fractions  of  the  pint,  and  proceed  in 
manner  as  above  directed.  So  likewise,  the  vessel  can  be  gra- 
duated to  pint  divisions,  in  number  as  many  as  its  capacity  will 
admit,  by  multiplying  the  weights  of  water,  and  adding  them 
to  those  previously  measured,  noting  the  level  of  each  with  the 
diamond. 

The  imperial  pint  is  larger  than  the  wine  pint  of  16  fluid- 
ounces,  in  the  ratio  of  6  to  5,  and,  therefore,  its  subdivisions  must 
number  20,  and  severally  of  1-73296  cubic  inches  capacity.  This 
makes  a  discrepancy,  the  inconvenience  of  which  can  be  remedied 
by  having  a  second  scale  upon  the  same  glass,  showing  their  rela- 
tive values.  The  only  disadvantage  is  the  trouble  of  a  second 
graduation,  which  is,  however,  compensated  for  in  the  conveni- 
ence of  the  first  scale,  each  division  of  which,  unlike  the  fluid- 
ounce  of  the  wine  pint,  represents  a  fluid-ounce  exactly,  weighing 
one  ounce  avoirdupois  of  distilled  water=437'5  grains. 

The  plan  of  graduating  the  pint,  itself  estimated  as  above,  into 
its  subdivisions  by  apportioning  its  height  into  the  requisite  num- 
ber of  equal  parts,  by  means  of  a  rule,  will  only  answer  for  ves- 
sels of  uniform  diameter  throughout,  and  which  are  only  intended 
for  the  grosser  operations  of  measuring. 

Those  graduates,  which  are  intended  for  nice  purposes,  should 
also  have  a  third  scale  graduated  in  cubic  inches.  The  cubic 
inch  equals  252-468  grains  of  distilled  water,  at  temperature  and 
pressure  the  same  as  above,  and  a  measure  or  bottle  of  this  ca- 
pacity should  be  prepared  and  kept  ready  for  use.  As  there  is 
sufficient  room  upon  the  glass  for  all  these  scales  without  the 
necessity  of  crowding  them  together, — there  should  be  an  equal 
interval  between  them. 

To  graduate  a  vessel  to  the  litre  of  the  French  standard,  sub- 
stitute 1  kilogramme  for  the  8750  grains  distilled  water,  and 
proceed  as  above,  making  the  subdivisions  pro  rata. 

The  graduates  and  cubic  inch  bottles  are  less  to  be  relied  on 
when  purchased  than  when  carefully  graduated  by  the  operator 
himself,  and  they  should  never  be  used  in  important  experiments 
without  having  been  previously  verified. 

For  the  graduation  of  the  ounce  and  drachm  measures,  and, 
indeed,  all  vessels  of  small  diameters  and  capacities,  such  as 
tubes  and  the  like,  the  divisions  of  which  must  necessarily  for 


196  GRADUATION    OP   VESSELS. 

want  of  space  closely  approximate  to  each  other,  mercury  is  much 
preferable  to  water.  Mercury  gives  a  more  level  and  distindt 
surface  than  water,  and  not  being  attracted  by  the  sides  of  the 
vessel,  allows  a  greater  accuracy  in  making  the  subdivisions, 
especially  in  very  narrow  tubes.  The  addition  of  one  grain  of 
lead  to  every  4000  grains  of  quicksilver  flattens  the  surface, 
and  greatly  facilitates  the  reading  of  thfe  level ;  but  it  must  be 
otherwise  pure  and  free  from  dross  and  film.  A  cubic  inch  of  pure 
mercury,  according  to  Faraday,  weighs  3425*35  grains,  at  62°  F. 

There  should  be  a  series  of  these  graduated  glasses,  ranging 
from  a  double  pint  down  to  a  drachm. 

For  the  tubes  and  other  vessels  used  in  analytic  research,  the 
decimal  divisions  are  both  convenient  and  necessary.  If  a  cubic 
inch  is  to  be  divided  into  tenths  and  hundredths,  the  former  are 
graduated  by  the  space  occupied  in  the  tube  by  the  one-tenths 
(342*50  grs.)  of  a  cubical  inch  of  mercury,  and  each  tenth  divi- 
sion coincident  with  the  level  of  the  metal  within,  is  marked  upon 
the  scale  with  the  file  or  writing  diamond.  So  also,  in  like  man- 
ner, are  the  hundredths  graduated  by  substituting  34-25  grs. 
(the  hundredth  of  a  cubic  inch  at  62°)  for  the  342-50  grs.  mercury. 

To  give  a  clear  idea  of  the  mode  of  preparing  a  measure  with 
mercury,  let  us  suppose  that  a  tube  is  to  be  graduated  to  cubic 
centimetres  of  the  French  standard.  In  the  first  place,  a 
narrow  strip  of  white  paper,  with  a  line  ruled  down  its  centre,  is 
to  be  pasted  lengthwise  upon  the  side  of  the  glass  to  be  gradu- 
ated, the  length  of  the  paper  of  course  corresponding  with  the 
height  of  the  glass.  13-59  grammes  of  mercury  are  next  to  be 
accurately  weighed  out,  and  this  quantity,  which  represents  a 
cubic  centimetre,  is  to  be  poured  into  the  tube,  held  vertically  by 
a  support  similar  to  A,  in  Fig.  115.  After  the  vessel  has  stood 
long  enough  for  the  liquid  to  become  quiet  and  assume  a  smooth 
surface,  its  level  is  noted  down,  and  its  corresponding  height 
marked  with  ink  upon  the  paper  slip.  The  space  which  this 
bulk  of  quicksilver  occupies  in  the  tube  equals  a  cubic  centimetre, 
and  when  accurately  noted,  may  serve  as  a  standard  for  the  gra- 
duation of  vessels  of  larger  capacity ;  for  these  cubic  centimetral 
divisions  can  be  multiplied,  merely  by  multiplying  this  given  bulk 
of  mercury,  and  noting  and  marking  upon  the  paper  the  level  of 
each  addition  as  its  surface  becomes  smooth.  Ten  times  the 


GRADUATION    OF   TUBES.  197 

i  * 

above  weight  of  mercury  gives  a  decimetral  division,  and  one- 
tenth  of  it  a  millimetral  division,  and  thus  we  have  an  easy  mode 
of  enlarging  or  diminishing  the  subdivisions  of  the  scale.  The 
ink  marks  are  subsequently  sunk  into  the  glass  with  the  diamond 
or  file,  or,  still  better,  by  the  action  of  fluoric  acid,  as  will  be 
described  directly. 

By  having  the  tubes  accurately  graduated  so  that  their  divi- 
sions exactly  correspond  with  the  weights  of  the  balance,  we 
acquire  the  convenience  of  calculating  at  once  the  weight  of  gases 
from  their  measured  volume. 

The  plan  of  consecutive  weighings,  involves  a  good  deal  of 
trouble  and  labor  where  large  vessels  are  being  prepared,  and 
hence,  in  such  cases,  the  convenience  of  this  mode  of  multiplying 
the  divisions  by  an  accurately  adjusted  measure. 

In  marking  the  scale,  let  those  lines  designating  the  tenths  ex- 
tend in  width  a  little  beyond  those  denoting  the  twentieths,  and 
these  latter,  in  their  turn,  a  little  beyond  those  expressing  the 
hundredths.  Fig.  101  represents  a  graduated  glass  with  a  pro- 
perly written  scale,  upon  which  the  tenths  are  shown  by  figures. 

As  these  glasses  are  to  be  standard  graduates  for  a  variety  of 
purposes  in  the  laboratory,  the  scale  should  be  indelible,  or 
etched  upon  the  glass.  For  this  purpose  the  paper  scale  must  be 
covered  with  a  thin  transparent  film  of  melted  white  wax.  When 
the  wax  has  cooled  and  hardened,  the  lines  and  figures  are  graved 
out  of  the  paper  with  a  sharp-pointed  style  or  burin,  and  the  ex- 
posed surfaces  of  the  glass  subjected  to  the  action  of  fluohydric 
acid,  as  directed  at  p.  79.  This  done,  and  the  wax  scraped  off, 
the  etched  portions  show  out  distinctly,  and  are  better  defined 
than  if  they  had  been  scratched,  as  is  sometimes  done,  with  the 
diamond-point  or  file. 

Be  careful  that  the  subdivisions  conform  accurately  among 
themselves,  and  in  the  aggregate  precisely  with  their  integer. 
The  volumes,  as  expressed  by  the  lines  on  the  scale,  should  also 
exactly  agree  with  their  corresponding  weights,  for  upon  these 
conditions  depends  the  accuracy  of  results. 

Tubes  for  eudiometry,  Fig.  103,  and  proof-glasses  for  alkali- 
metry, Fig.  104,  and  all  other  vessels  used  in  chemical  operations 
for  measuring,  are  graduated  in  like  manner.  The  bell  glasses 
(Fig.  85)  for  which  and  all  large  vessels,  water  is  preferable, 


198 


GRADUATED    VESSELS. 


should  be  graduated  into  double  cubic  centimetres,  so  that  every 
divisional  line  may  correspond  to  two  centimetres ;  and  the  tubes 
into  double  cubic  millimetres,  so  that  every  line  may  correspond 
to  two  cubic  millimetres. 


Fig.  103. 


Fig.  104. 


Fig.  105. 


Dr.  Henry  proposes,  as  a  quick  and  accurate  method  of  gradu- 
ating tubes  for  eudiometry,  &c.,  to  have  a  standard  tube,  0-08  of 
an  inch  in  diameter,  and  carefully  divided  into  10  equal 
parts?  Of  10  grains  of  mercury  (60°  F.)  capacity  each. 
This  tube  (Fig.  105)  is  a  graduated  pipette,  fitted  with 
a  stop-cock  and  air-screw  to  promote  its  efficiency.  It 
serves  to  measure  or  weigh  out  a  standard  measure  of 
mercury  in  successive  tenths  or  hundredths,  as  may  be 
required,  and  according  as  it  may  be  graduated. 

The  vessels  should  be  of  clear  glass.  The  tubes  must 
be  thick,  and  strong  enough  to  support  the  weight  of 
their  full  contents  of  mercury.  For  the  convenience  of 
closing  their  mouths  with  glass  disks,  their  ends  may  be 
ground  flat  and  even. 

In  all  operations  of  graduation,  the  waste  of  mercury 
is  avoided  by  working  over  a  porcelain  plate,  or,  what  is 
better,  the  mercury  trough,  Fig.  115.  The  metal  may 
be  conveyed  to  the  vessels  in  the  pipette,  Fig.  107, 
which  enables  the  addition  or  removal  of  minute  por- 
tions, as  the  case  may  require. 


GRADUATED   VESSELS. 


199 


The  requirements  of  the  laboratory  call  for  an  assorted  stock 
of  graduated  tubes  and  proof-glasses,  varying  in  diameter  from  a 
quarter  to  two  inches. 

Below  is  a  useful  table,  showing  the  value  of  the  measures  of 
capacity  in  cubic  inches,  grains,  and  as  compared  with  apothe- 
caries' measure. 


Grains  of  dis- 

Apothecaries' 

Cubic  inches. 

tilled  water. 

measure. 

Imperial  gallon,     . 

277-274 

70000 

9-966  -f- 

Imperial  pint,         .  " 

34-65925 

8750 

Imperial  fluidounce, 

1-7329625 

437-5 

The  old  wine  pint, 

28-8827 

7291-666 

16  fl.  oz.    . 

Old  fluidounce, 

1-805169 

455-73 

8  drachms. 

Cubic  inch,        '  -v'.     •*. 

1- 

252-458 

Litre,    . 

61-02525 

15406-312 

2-1135  pints. 

Decilitre,       .         .      ••.-'. 

6-10252 

1540631 

3-3816  fl.  oz. 

Centilitre,     .         .     .  >/ 

0-61025 

154-063 

2-7053  fl.  drachms. 

Millilitre,      .        ,?f  ""'•'•*' 

0-06102 

15-406 

16-2318  minims. 

Pipettes. — These  are  tubes  for  measuring  liquids  in  drops,  and 
consist  wholly  of  glass,  blown  after  either  of  the  forms  shown  by 
Figs.  106, 109.  The  lower  and  capillary  end  of  the  pipette  being 

placed  in  the  liquid,  is  to  be  closed  at  the  upper 
^lg'  106'  end  by  the  thumb,  as  soon  as  the  liquid  in  the  Fig'  107> 
bore  has  reached  the  level  of  that  in  the  con- 
taining vessel.  It  is  next  brought  immediately 
over  thfc  receiving  vessel  in  which  it  is  to  be 
wholly  or  partly  emptied,  when  the  thumb  is 
alternately  raised  and  lowered  until  a  sufficient 
number  of  drops  has  been  forced  out  by  atmo- 
spheric pressure  to  make  up  the  volume  or 
weight  required,  as  the  case  may  be.  If  the  bore  is 
too  large,  the  liquid  will  run  out  in  a  thin  stream, 
instead  of  drops.  As  the  liquid  rises  in  the  bore  of  the 
pipette  in  proportion  to  the  pressure  of  the  external 
liquid,  the  deeper  it  is  plunged  into  the  containing 
vessel  the  greater  the  amount  it  will  draw  up. 

The  flow  of  the  liquid  is  completely  under  the  control 
of  the  operator,  it  being  only  necessary  to  press  down 
the  thumb  upon  the  mouth,  to  stop,  completely,  the  dropping 
from  the  lower  end.  The  above  patterns  are  designed  for  very 
small  operations.  To  be  convenient  for  large  quantities  of  li- 


200 


PIPETTES. 


.  108. 


quid,  they  should  be  blown  from  a  tube  ten  inches  long,  and  with 
an  inch  bulb  above  the  centre, 
as  shown  by  Fig.  108,  so  as  to       Fig-  m 
form  a  reservoir. 

This  pipette  may  be  filled  by 
applying  the  mouth  to  the  upper 
end,  and  sucking  in  the  liquid ; 
but  the  method  is  disagreeable  to 
the  operator  when  acid  or  other 
noxious  fumes  are  natural  to  the 
liquid,  and   moreover   it   intro- 
duces moisture.    The  better  plan, 
in  such  cases,  is  to  make  the 
pipette  by  drawing  out  the  lower 
end  of   a   tube   to   a   capillary 
opening,  and  widening  the  upper, 
and  then  stretching  a  piece  of 
india-rubber  cloth  tightly  over 
the  top,  as  shown  by  Fig.  109 ;  or,  more  easily 
still,  covering  the  bulb-pipette,  at  its  top,  with  a 
caoutchouc  ball.    By  compressing  the  bottle  with 
the   hand,  or   pressing  against  the  india-rubber 
cover  with  the  thumb,  the  air  within  the  implement  is  partially 
forced   out,  and  the  liquid  into 
which  the  pipettes  are  plunged 
immediately  runs   in   to  fill   its 
place.     The  india-rubber  having 
then  regained  its  original  state 
of  distension  by  means  of  the  up- 
ward pressure  of  the  atmosphere, 
retains  the  liquid  so  completely 
that  not  a  drop  drains  off  until 
expelled  by  again  pressing  the  bag  or  cover. 

Another  form  of  implement  for  measuring  drops  of 
liquid  is  Schuster's  alkalimeter,  shown  by  Fig.  110. 
It  is  a  glass  bottle,  of  1  oz.  capacity,  with  a  ground 
stopper,  from  which  the  liquid  issues  dropwise,  when 
the  admission  of  air  is  properly  adjusted  by  means  of 
the  stopper,  which  should,  for  that  purpose,  be  held  loosely  in  its 
place,  and  not  lifted  entirely  out. 


Fig.  110. 


GRADUATED    PIPETTES. 


201 


Fig.  112. 


Graduated  pipettes  are  also  used  for  dropping  definite  quantities, 
with  great  precision.    One,  with  caoutchouc  cover,  is  very  intelligi- 
bly represented  by  Fig.  111.  Another  form,  and  that  which  is  much 
used  in  volumetric  analysis,  is  shown  by  Fig.  112.    It  is  known  as 
Mohr's  Dropping-tube,  and  consists  of  a  glass  tube  drawn  out  to 
a  capillary  opening  at  the  lower 
end,  and  graduated  into  100°  Fig- 113> 
or  divisions.     To  the  capillary 
orifice  a  short  piece  of  vulcan- 
ized india-rubber  tubing  is  at- 
tached, and  in  the  lower  end  of 
this,  again,  is  inserted  a  short 
conical  piece  of  glass  tubing, 
which  forms  the  spout  through 
which    the    liquid   is   to   flow. 
Clasping  the  india-rubber  neck 
is  a  bent  wire,  which  so  com- 
presses it  as  to  make  a  water- 
tight joint;  when,  however,  the 
grasp  is  relaxed  by  pressing  the 
projecting  ends  of  the  wires  be- 
tween the  thumb  and  fingers, 
the   liquid    flows   through    the 
neck  dropwise,  in  slow  or  quick 
succession,    according    as    the 
pressure  is  gentle  or  strong,  the  flow  being 
controlled  by  this  means. 

Some  chemists  prefer  to  use  syringes 
for  measuring  liquids  in  drops,  and  these 

instruments  are  of  glass,  and  as  presented  by  Fig.  113.  The 
liquid  is  drawn  into  them  by  immersing  the  lower  end  in  the  con- 
taining vessel  and  raising  the  piston.  On  pressing  the  top  of 
the  piston  with  the  thumb,  the  liquid  is  driven  out  again,  in 
quantity  proportional  to  the  force  employed,  a  gentle  depression 
expelling  it  dropwise  and  slowly.  The  stratum  of  air  between 
the  piston  and  surface  of  the  liquid,  as  represented  in  the  draw- 
ing, assists  the  action. 

When  the  barrel  of  the  syringe  is  graduated,  like  that  shown 
in  the  figure  which   exhibits  Alsop's  minimeter,  it  allows  the 


202 


MEASUREMENT    OF    GASES. 


Fig.  114. 


transfer  of  a  given  quantity  of  liquid  from  one  vessel  to  another 
at  a  single  operation.  To  this  end,  it  is  only  necessary  to  adjust 
the  motion  of  the  piston,  so  as  to  exactly  draw  in  the  required 
measure ;  and  if  an  excess  should  be  accidentally  taken  up,  to 
gently  depress  the  piston  until  it  is  expelled  and  the  barrel  is 
filled  only  to  the  proper  degree  or  division. 

MEASUREMENT  OF  GASES.* — In  measuring  a  required 
volume  of  any  gas,  a  graduated  tube,  like  the  one  shown 
in  Fig.  114,  is  first  filled  with  mercury  or  water,  as  the 
case  may  be,  in  the  pneumatic  trough,  and  placed  upon 
the  shelf.  When  the  tube  is  too  slender  to  sustain  itself 
in  an  upright  position,  it  is  then  convenient  to  use  the 
clamp  and  support  A,  Fig.  115.  If  the  mouth  of  the 
receptacle  of  the  gas  is  wide,  it  is  necessary,  before  trans- 
ferring to  the  graduating  tube,  to  place  a  small  funnel  in 
its  submerged  end,  so  that  the  ascending  bubbles  may  be 
received  upon  a  larger  surface.  By  giving  the  reservoir, 
generally  a  bell  glass,  a  slightly  inclined  position,  so  that 
the  edge  of  its  mouth  may  reach  under  the  funnel,  the 
transfer  is  made  easily  and  without  loss.  As  soon  as 
the  requisite  quantity  has  been  transferred,  the  connection  must 

be  broken,  and  both  the 
bell  and  tube  made  to 
resume  their  former  po- 
sitions on  the  shelf. — 
(See  Transfer  of  Cras- 
es.)  The  tube  is  then 
to  be  depressed  in  the 
trough  until  the  metal, 
inside  and  outside,  is  at 
the  same  level.  This 
mode  subjects  the  gas 
only  to  atmospheric 
pressure,  but  the  tube 
must  be  held  by  a  cork- 
lined  clamp,  as  in  Fig. 


Fig.  115. 


*  See  Regnault's  Chemistry,  and  article  EUDIOMETER  in  Handworterbuch  der 
Chemie.  The  latter  explains  the  details  of  Bunsen's  method  for  graduating  tubes 
and  measuring  gases. 


MEASUREMENT   OF   GASES.  203 

115,  or  linen  holder,  and  not  in  the  naked  hand,  the  warmth  of 
which,  by  expanding  the  gas,  would  be  a  source  of  error. 

It  is  very  difficult  to  transfer  a  quantity  of  gas  exactly  corre- 
sponding with  a  division  of  the  tube  at  one  trial — several  attempts 
are  requisite,  except  in  cases  of  consummate  manipulation.  It  is 
perhaps  better  to  transfer  the  last  portions  from  a  small  tube. 
The  gas  passing  through  very  slowly  and  in  fine  bubbles  can,  by 
this  arrangement,  be  stopped  off  as  soon  as  the  volume  which  has 
entered  accords  with  the  division  indicated.  When  more  than 
sufficient  has  been  transferred,  place  the  first  finger  upon  the 
mouth  of  the  tube  so  as  to  leave  a  partial  opening,  and  incline  it 
sufficiently  to  allow  the  exit  of  the  redundant  gas.  Examine  anew 
the  contained  volume,  and  if  it  is  still  in  excess,  repeat  this  ope- 
ration until  the  level  of  the  liquid  reaches  the  proper  height. 

To  insure  accuracy  in  the  comparison  of  volumes  of  different 
gases,  they  must  necessarily  be  measured  at  the  same  temperature 
and  under  the  same  pressure.  The  proof-glasses  in  which  they 
are  estimated,  should  be  kept  out  of  the  influence  of  unequal 
warmth  during  the  process,  for  the  action  of  heat  upon  the  volume 
of  gases  is  a  cause  of  considerable  error. 

In  order  to  determine  with  precision  the  exact  height  which 
the  water  or  mercury  assumes,  the  vessel  should  be  placed  at  re- 
pose upon  a  level  shelf,  and  the  eye  directed  on  a  line  with  the 
surface  of  the  fluids,  and  the  height  read  off  accordingly.  This 
notation  requires  some  care  and  precision,  for  as  mercury  assumes 
a  convex  surface,  owing  to  its  own  cohesion,  and  water  a  concave 
one,  because  of  the  attraction  for  the  walls  of  the  tube,  especially 
in  narrow  cylinders,  the  curve  thus  occasioned  presents  an  impedi- 
ment to  the  ready  determination  of  the  exact  level.  To  provide 
against  the  action  of  the  heat  of  the  body,  it  is  better  to  read  at 
a  distance  of  several  yards,  through  a  spy-glass. 

"When  water  is  the  confining  fluid,  read  the  real  surface  in  the 
middle  of  the  dark  zone  formed  by  the  water  around  the  inner 
walls  of  the  tube ;  on  the  other  hand,  when  mercury  is  used, 
"place  the  real  surface  in  a  line  drawn  exactly  in  the  centre 
between  the  highest  point  of  the  surface  of  the  mercury  and  the 
points  at  which  the  latter  is  in  actual  contact  with  the  walls  of 
the  tube." 

In  either  case  the  temperature  of  the  fluid  and  gas  should  be 


204  MEASUREMENT    OF  GASES. 

uniform.  When  the  bulk  of  the  containing  fluid  is  sufficient  to 
allow  the  entire  immersion  of  the  cylinder,  this  is  easily  effected ; 
otherwise,  it  becomes  necessary  to  equalize  the  temperature  of 
the  surrounding  air,  by  keeping  the  cylinder  exposed  to  both,  in 
order  to  determine  accurately  the  degree  of  the  scale  at  which 
the  mercury  or  water  stands. 

Another  important  matter,  as  before  mentioned,  in  the  com- 
parison of  volumes  of  different  gases,  is  the  necessity  of  uniform 
pressure,  in  their  measurement.  If  the  level  of  the  containing 
fluid  within  and  without  the  cylinder  exactly  corresponds,  the 
pressure  upon  it  is  directly  shown  by  the  barometer.  A  higher 
level,  internally,  indicates  less  pressure,  and  vice  versa:  when 
the  fluid  stands  higher  outside  of  the  cylinder  than  within  it,  the 
level  may  be  restored  by  raising  the  tube ;  in  the  opposite  case, 
by  depressing  the  tube.  These  operations  of  adjusting  the  level 
are1  more  difficult  when  mercury  is  the  containing  fluid.  In 
operations  occupying  much  time,  the  barometer  should  be  fre- 
quently consulted,  so  as  to  guard  against  any  alteration  sufficient 
to  impair  the  results. 

Ker's  tube,  constructed  for 
the  measurement  of  gas  at  the 
time  of  its  disengagement,  is 
shown  by  Fig.  116.  The  branch 
a,  ten  inches  in  length,  glass 
stoppered  and  graduated  to  two 
cubic  inches,  is  the  recipient  of 
the  gas  disengaged  from  the 

material  in  the  bulb  c,  by  the  action  of  a  reagent  introduced  in 
the  other  branch  6.  The  gas  collecting  in  a  is  there  measured 
by  the  scale,  previous  to  being  transferred  for  examination. 


MEASUREMENT   OF   TEMPERATURE. 


205 


CHAPTER  X. 


MEASUREMENT    OF   TEMPERATURE. 

TEMPERATURE  is  estimated  by  means  of  two  instruments,  the 
pyrometer  and  thermometer,  the  action  of  which  is  based  upon 
the  relative  expansibility  of  bodies  under  the  influence  of  heat 
and  cold.  They  do  not  therefore  indicate  the  amount  of  heat 
contained  in  the  body,  but  only  the  comparative  temperature  of 
two  or  more  bodies. 

The  Pyrometer. — This  instrument  is  rarely  used  in  the  ordi- 
nary operations  of  the  laboratory,  it  being  only  applicable  to  the 
measurement  of  heats  more  intense  than  can  be  borne  by  thermo- 
meters. Pyrometers  are  constructed  of  solid  substances,  though 
gaseous  bodies,  on  account  of  their  sensitiveness  to  heat  or  cold 
and  greater  uniformity  of  expansion,  would  be  preferable.  Wedg- 
wood's Pyrometer  is  the  oldest  invention,  but  Daniell's  instru- 
ment is  the  most  approved,  and  by  skilful  management  may  be 
made  to  give  accurate  indications.  Its  principal  application  is  in 
furnace  operations.  In  assaying,  where  the  required  tempera- 
ture varies  with  the  metal  under  process,  it  is  particularly  avail- 
Fig.  117. 


able  in  determining  the  heat  of  the  furnace ;  for  much  of  the 
accuracy  of  the  assay  depends  upon  the  temperature  at  which  it 
is  made.  Fig.  117  represents  the  apparatus. 


206  THE   PYROMETER. 

"  It  consists  of  two  parts,  which  may  be  distinguished  as  the 
register  1,  and  the  scale  2.  The  register  A,  is  a  solid  bar  of 
blacklead  earthenware  highly  baked.  In  this  a  hole  a  a,  is 
drilled,  into  which  a  bar  of  any  metal,  six  inches  long,  may  be 
dropped,  and  which  will  then  rest  upon  its  solid  end.  A  cylin- 
drical piece  of  porcelain  c,  called  the  index,  is  then  placed  upon 
the  top  of  the  bar,  and  confined  in  its  place  by  a  ring  or  strap  of 
platinum  d,  passing  round  the  top  of  the  register,  which  is  partly 
cut  away  at  the  top,  and  tightened  by  a  wedge  of  porcelain  e. 
When  such  an  arrangement  is  exposed  to  high  temperature,  it  is 
obvious  that  the  expansion  of  the  metallic  bar  will  force  the  index 
forward  to  the  amount  of  the  excess  of  its  expansion  over  that  of 
the  blacklead,  and  that  when  again  cooled  it  will  be  left  at  the 
point  of  greatest  elongation.  What  is  now  required,  is  the 
measurement  of  the  distance  which  the  index  has  been  thrust 
forward  from  its  first  position,  and  this,  though  in  any  case  but 
small,  may  be  effected  with  great  precision  by  means  of  the 
scale." 

"  This  is  independent  of  the  register,  and  consists  of  two  rules 
of  brass,//  and  #,  accurately  joined  together  at  a  right  angle  by 
their  edges,  and  fitting  square  upon  the  two  sides  of  the  black- 
lead  bar.  At  one  end  of  this  double  rule,  a  small  plate  of  brass 
A,  projects  at  a  right  angle,  which  may  be  brought  down  upon 
the  shoulder  of  the  register  formed  by  the  notch  cut  away  for  the 
reception  of  the  index.  A  movable  arm  D  is  attached  to  this 
frame,  turning  at  its  fixed  extremity  on  a  centre  i9  and  at  its 
other  carrying  the  arc  of  a  circle,  whose  radius  is  exactly  five 
inches,  accurately  divided  into  degrees,  and  thirds  of  a  degree. 
Upon  this  arm,  at  the  centre  of  the  circle  &,  another  lighter  arm 
c,  is  made  to  turn,  one  end  of  which  carries  a  nonius  H  with  it, 
which  moves  upon  the  face  of  the  arc,  and  subdivides  the  for- 
mer graduation  into  minutes  of  a  degree ;  the  other  end  crosses 
the  centre  and  terminates  in  an  obtuse  steel  point  m,  turned  in- 
wards at  a  right  angle. 

"  When  an  observation  is  to  be  made,  a  bar  of  platinum  or 
malleable  iron  is  placed  in  the  cavity  of  the  register ;  the  index 
is  to  be  pressed  down  upon  it,  and  firmly  fixed  in  its  place  by 
the  platinum  strap  and  porcelain  wedge.  The  scale  is  then  to  be 
applied  by  carefully  adjusting  the  brass  rule  to  the  sides  of  the 


THERMOMETERS.  207 

register,  and  fixing  it  by  pressing  the  cross-piece  upon  the 
shoulder,  and  placing  the  movable  arm  so  that  the  steel  part  of 
the  radius  may  drop  into  a  small  cavity  made  for  its  reception, 
and  coinciding  with  the  axis  of  the  metallic  bar.  The  minute  of 
the  degree  must  then  be  noted  which  the  nonius  indicates  upon 
the  arc.  A  similar  observation  must  be  made  after  the  register 
has  been  exposed  to  the  increased  temperature  which  it  is  de- 
signed to  measure,  and  again  cooled,  and  it  will  be  found  that 
the  nonius  has  been  moved  forward  a  certain  number  of  degrees 
or  minutes.  The  scale  of  this  pyrometer  is  readily  connected 
with  that  of  the  thermometer  by  immersing  the  register  in  boil- 
ing mercury,  whose  temperature  is  as  constant  as  that  of  boiling 
water,  and  has  been  accurately  determined  by  the  thermometer. 
The  amount  of  expansion  for  a  known  number  of  degrees  is  thus 
determined,  and  the  value  of  all  other  expansions  may  be  con- 
sidered as  proportionate." 

"  The  following  is  a  list  of  the  melting-points  of  some  of  the 
metals,  and  it  is  obvious  that  in  an  assay  of  each  particular 
metal,  the  temperature  employed  must  exceed  by  a  considerable 
number  of  degrees  its  melting-point.  The  table  is,  therefore, 
very  useful. 

Fahrenheit 

Tin  melts  at        .  .  .'.'         .  ..        v  .;  .         '.         422° 

Bismuth,        ,  '          .'        -— ^        •>    ^ ,  ^  ^  407 

Lead,      .   _•«       .  '.;'•          ..        '     .         '  ..%         '  '.  -.      612 

Zinc,  t.          -  ».  .  .  '  .         .-   ; •  jj  773 

Cadmium,  .  \         »,. ,       .    +t'.     '     ,.  „  •      \   .         442 

Silver,  .  7  .  * .  £     .    »  I860 

Copper,  ;*  v.       -  *  '•  .        -'-•••       'yV      1996 

Gold,  .         ••:.••   ;        .  .*         Y  .  ,]        2016 

Cast  iron,  .         '    .•  '         .  .^',  «V        .       2786 

Cobalt  and  nickel  rather  less  fusible  than  iron." 

Daniell. 

Thermometers. — A  thermometer  consists  of  a  graduated  cylin- 
drical stem,  with  a  uniform  capillary  bore,  having  one  of  its  ends 
blown  into  a  bulb  and  filled  with  mercury  or  alcohol,  and  the 
other  hermetically  closed,  the  space  above  the  column  of  fluid 
being  a  vacuum,  or  as  nearly  as  possible  devoid  of  air. 

Mercury,  on  account  of  its  greater  equability  of  expansion, 
and  of  its  boiling-point  being  as  high  as  650°  F.,  is  more  avail- 
able in  the  construction  of  thermometers  for  measuring  tempera- 


208 


MEASUREMENT   OF  TEMPERATURE. 


tures  exceeding  that  of  boiling  water  (212°  F.)  Alcohol,  on  the 
other  hand,  by  reason  of  its  eminent  property  of  dilatation  is 
more  applicable  for  determining  temperatures  lower  than  the 
freezing-point  of  mercury,  its  point  of  congelation  being  as  far 
down  as  —90°  F. 

The  two  points  of  graduation  are  the  freezing  and  boiling 
points  of  water,  the  interval  between  each  being  differently  appor- 
tioned, according  as  the  scale  of  Fahrenheit,  Celsius,  or  Reaumur 
(the  three  most  in  use)  is  employed. 

Fahrenheit's  scale  ranges  from  32°  to  212° ;  that  of  Celsius 
(centigrade)  from  0°  to  100°  ;  Reaumur's  from  0°  to  80°.  The 
first  is  most  popular  in  England  and  in  this  country ;  the  second 
in  France,  and  the  third  in  Russia,  Spain,  and  part  of  Germany. 
The  scale  of  Fahrenheit  has  its  zero  at  32°  below  the  freezing- 
point  of  water,  and  the  other  two  exactly  at  that  point.  There- 
fore, in  comparing  the  degrees  of  the  former  with  those  of  the 


Fahrenheit's 
Scale. 


Fig.  118. 

Centi?rade 
Scale. 


Reaumur's 
Scale. 


212 

192 

152 

152 

112 

S2 

72 

52 

32    . 


100 

80 

60 

40 

20 

0 


latter,  the  negative  or  those  below  zero  have  a  prefix  of  the 
minus  ( — )  sign,  and  the  positive  or  those  above,  the  plus  (-f ) 


THERMOMETERS.  209 

sign.     The  diagram  (Fig.  118)  will  present  the  relative  position 
of  the  corresponding  degrees  of  the  three  scales. 

The  following  rules  will  be  found  convenient  for  translating 
the  degrees  of  one  scale  into  those  of  another  : 

1.  To  reduce    Centigrade   degrees  to   those   of  Fahrenheit, 
multiply  by  9,  and  divide  by  5,  and  to  the  quotient  add  32,  that 
is,— 

Cent  X  9  +  32  =  Fahr. 
5 

2.  To  reduce  Fahrenheit's  degrees  to  Centigrade  : 


y 

8.  To  reduce  Reaumur's  to  Fahrenheit's  :  — 


4.  To  convert  Fahrenheit's  to  Reaumur's  :  — 

Fahr.  —  32  X  4 
-  g  -  =  Reaumur. 

A  slender  stem  and  precise  uniformity  of  bore  are  indispensable 
to  the  accuracy  of  a  thermometer.  The  tube  must  also  be  en- 
tirely void  of  air,  as  is  known  when,  on  being  inverted,  the  con- 
tained mercury  makes  a  free  and  rapid  descent.  Moreover,  the 
graduation  of  the  scale  must  be  verified,  and  to  do  this,  the  bulb 
is  immersed  in  a  mixture  of  salt  and  snow  to  test  the  accuracy  of 
its  freezing  degree,  and  afterwards  in  boiling  water  (under  the 
ordinary  pressure  of  the  atmosphere)  to  observe  its  boiling-point. 
If  in  either  case  when  the  fluid  becomes  stationary,  after  suffi- 
cient delay  for  the  bulb  to  accquire  the  temperature  of  the  bath, 
it  corresponds  with  the  degree  marked  upon  the  scale,  its  gradua- 
tion as  regards  the  freezing  and  boiling  points  is  correct.  To 
determine  the  exactness  of  the  intermediate  space,  the  length  of 
the  interval  is  measured  with  a  pair  of  compasses,  and  it  is  then 
easy  to  ascertain  by  means  of  an  accurate  ruler,  if  the  divisions 
accord  with  each  other,  and  in  the  aggregate  with  the  total  length 
of  the  scale. 

For  measuring  temperatures  higher  than  580°  F.,  the  top  of 
the  thermometer  should  be  unsealed  and  the  mercury  exposed  to 

14 


210 


MEASUREMENT   OF  TEMPERATURE. 


Fig.  119.  the  pressure  of  the  atmosphere,  for 
if  hermetically  closed,  it  will  boil  at 
that  point  and  burst  the  tube. 

The  tube,  as  before  said,  should 
be  as  slender  as  possible,  and  not  too 
long,  otherwise  in  testing  shallow 
solutions  in  ebullition,  that  part  of 
the  stem  which  is  above  the  liquor 
is  exposed  to  the  heat  of  the  rising 
vapor,  and  as  the  expansion  to  mer- 
cury within  would  be  thus  estimated 
with  that  of  the  contents  of  the  bulb, 
the  only  part  heated  at  the  time  of 
graduation,  incorrect  conclusions 
would  be  drawn. 

In  ascertaining  the  condition  of  a 
liquid  with  regard  to  heat  or  cold, 
the  thermometer  is  gradually  intro- 
duced into  it,  moved  around  it  seve- 
ral times  so  as  to  produce  an  equable 
diffusion  of  temperature,  and  after 
the  mercury  has  become  stationary 
at  a  certain  point,  the  degree  coinci- 
dent with  that  point  is  noted  down 
as  the  temperature. 

The  scales  of  thermometers  are 
most  generally  graduated  upon  a 
wooden  slip  or  support,  to  which  the 
stem  is  secured  by  clamps  and 
screws.  In  such  case,  the  scale  is 
hinged,  so  as  to  afford  convenience 
in  the  use  of  the  thermometer  for 
taking  the  boiling-point  of  solutions 
without  injury  to  the  scale. 

Thermometers  for  chemical  pur- 
poses should  be  wholly  of  glass  and 
cylindrical,  as  that  form  is  most  con- 
venient for  passing  through  tubulures; 
and,  moreover,  the  scales  should  be 


Fig.  120. 


THERMOMETERS.  211 

indestructible.  The  annexed  drawings  present  one  (Fig.  119) 
with  Celsius's  scale  etched  on  the  outside  by  fluorine,  and  another 
(Fig.  120)  with  a  black  letter  enamelled,  Fahrenheit,  scale  en- 
closed in  the  tube. 

The  scales  of  the  mercurial  thermometers  are  made  to  range 
as  high  as  600°  F.,  and  for  convenience  are  sometimes  graduated 
on  one  side  of  the  stem  with  the  Centigrade  and  on  the  other 
with  the  Fahrenheit  scale.  Fahrenheit's  degrees  being  small, 
have  the  advantage  over  the  others  of  not  giving  fractional  parts, 
which  are  inconvenient  in  calculation.  The  laboratory  should 
be  supplied  with  two  or  more  of  these  implements. 

Air  thermometers  are  sometimes  used,  and  though  very  deli- 
cate, are  less  convenient  than  those  of  mercury  and  alcohol,  and 
liable  to  objections  which  do  not  attach  to  the  latter. 

Leslie's  differential  thermometer,  Fig.  121,  which  is  a  modifi- 
cation of  the  air  thermometer,  is  now  frequent- 
ly used  in  researches  for  determining  very 
small  differences  in  temperature.     It  consists 
of  a  U  tube  with  a  hollow  bulb  blown  at  each 
end  and  closed,  so  that  the  fluid  within  (sul- 
phuric acid)  colored  with  carmine  to  render 
it  more  visible,  is  entirely  free  from  external 
atmospheric  pressure.     This  instrument  does 
not  exhibit  a  change  of  temperature  except  by 
the  difference  between  the  elasticity  of  the  air 
in  the  two  bulbs,  and  therefore  indicates  only 
such  temperatures  as  affect  one  bulb  and  not 
the  other.    When  both  bulbs  are  of  equal  temperature,  the  liquid 
within  remains  stationary ;  but  so  soon  as  one  becomes  warmer 
than  the  other  the  fluid  recedes  to  the  opposite  bulb,  and  the 
scale  attached  to  one  of  the  legs  is  so  graduated  as  to  measure 
the  comparative  degree  of  heat  thus  occasioned. 

Melloni's  thermo-multiplicator  (Muller,  p.  541),  is  another  in- 
strument for  the  indication  of  changes  of  temperature. 

Another  convenient  instrument,  especially  in  meteorological 
observations,  is  the  thermometrograph.  It  is  so  constructed  as 
to  register  the  maximum  and  minimum  temperatures  occurring 
during  an  interval,  and  hence  the  presence  of  the  operator  is  not 
necessary  to  note  them  at  the  moment  of  their  occurrence. 


212 


MEASUREMENT   OF   TEMPERATURE. 


The  apparatus  which  is  shown  in  Fig.  122,  consists  of  a  mer- 
curial and  a  spirit  thermometer  placed  horizontally  and  parallel 
to  each  other.  A  steel  pin  enclosed  in  the  tube  of  the  former  is 
pushed  before  the  column  of  mercury  when  the  metal  in  the  bulb 

Fig.  122. 


expands,  but  remains  fixed  when  it  again  recedes  on  cooling,  and 
thus  indicates  at  that  point  the  maximum  temperature  which  has 
occurred  during  any  interval. 

The  corresponding  rod,  enclosed  in  the  tube  of  the  spirit 
thermometer,  of  glass,  colored  to  render  it  more  visible,  is  not 
advanced  by  the  expansion  of  the  spirit,  but  retreats  with  the 
column  as  it  contracts  to  the  last  point  reached  by  it,  and  thus 
registers  the  minimum  of  temperature  during  a  certain  time,  at 
the  degree  coincident  with  its  inner  end. 

When  this  instrument  is  to  be  used,  it  must  be  inclined  in  such 
a  position  as  to  allow  the  steel  rod  to  descend  to  the  column  of 
mercury,  and  the  glass  rod  to  the  end  of  the  spirituous  column. 
The  arrangement  of  the  bulbs  in  opposite  positions  is  with  a  view 
to  this  object.  After  the  rods  have  reached  their  proper  situa- 
tions, we  may,  by  placing  the  instrument  horizontally  any  morn- 
ing or  evening,  obtain  at  the  end  of  the  following  24  hours,  the 
maximum  and  minimum  temperature  of  that  interval. 

There  are  some  very  excellent  remarks  by  Regnault  upon  the 
relative  advantages  of  the  different  modes  of  measuring  tempera- 
ture, to  which  the  student  may  advantageously  refer. 

The  translation  of  his  several  papers  on  the  subject,  is  to  be 
found  in  the  Franklin  Institute  Journal  for  1848. 

The  following  table  shows  the  corresponding  degrees  of  Fahren- 
heit's, Reaumur's,  and  the  Centigrade  thermometers. 


THERMOMETRICAL  EQUIVALENTS. 


213 


!* 

Reaumur. 

C  'O 

iu  a 
O  £, 

Fahren- 
heit. 

1 

.i  w 

I! 

Fahren- 
heit. 

Reaumur. 

i| 

<3& 

Fahren- 
heit. 

Reaumur. 

ii 

U& 

* 

600 

52-4 

315-5 

569 

238-6 

298-3 

539 

2253 

281  6 

508 

211-5 

264-4 

599 

52 

315 

568-4 

238-4 

298 

538-2 

225 

281-2 

507-2 

211-2 

264 

598 

51-5 

314-4 

568 

238-2 

297-7 

538 

224-9 

281-1 

507 

211-1 

2638 

567-2 

51-2 

314 

567-5 

238 

297-5 

537-8 

224-8 

281 

506-7 

211 

263-7 

597 

51-1 

3138 

567 

237-7 

297-2 

537 

224-4 

280-5 

506 

2106 

263-3 

596-7 

51 

313-7 

566-6 

237-6 

297 

536 

224 

280 

505-4 

210-4 

263 

596 

50-3 

3133 

566 

237-3 

296-6 

535 

2235 

279-4 

505 

210-2 

2627 

595-4 

250-4 

313 

565-2 

237 

296-2 

534-2 

223-2 

279 

504-5 

210 

262-5 

595 

'50-2 

3127 

565 

236-9 

296-1 

534 

223-1 

278*8 

504 

209-7 

262-2 

594-5 

250 

312-5 

564-8 

236-8 

296 

533-7 

223 

278-7 

503-6 

209-6 

262 

594 

249-7 

312-2 

564 

236-4 

295-5 

533 

222-6 

278-3 

503 

209-3 

261-6 

593-6 

2496 

312 

563 

236 

295 

532-4 

222-4 

278 

502-2 

209 

261-2 

593 

49-3 

311*6 

562 

235-5 

294-4 

532 

222-2 

277-7 

502 

2089 

261-1 

592-2 

249 

311-2 

561-2 

2352 

294 

531-5 

222 

2775 

501-8 

208-8 

261 

592 

248-9 

311-1 

561 

235  1 

293-8 

531 

221-7 

277-2 

501 

208-4 

260-5 

59T8 

248-8 

311 

560-7 

235 

293-7 

5306 

221-6 

277 

500 

208 

260 

591 

248-4 

310-5 

560 

234-6 

293  3 

530 

221-3 

2766 

499 

207-5 

259-4 

590 

248 

310 

559-4 

2344 

293 

529-2 

221 

276-2 

498-2 

207-2 

259 

589 

247-5 

309-4 

559 

234-2 

292-7 

529 

220-9 

276  1 

498 

207-1 

258-8 

588-2 

247-2 

309 

558  5 

234 

292-5 

528-8 

2208 

276 

497-7 

207 

2587 

588 

247-1 

308-8 

558 

233-7 

2922 

528 

220-4 

275-5 

497 

206-6 

2583 

587-7 

247 

308-7 

557-6 

233-6 

292 

527 

220 

275 

496-4 

206-4 

258 

587 

246-6 

308-3 

557 

233-3 

291-6 

526 

219-5 

274-4 

496 

2062 

257-7 

586-4 

246-4 

308 

556-2 

233 

291  2 

5'52 

219-2 

274 

495-5 

206 

257-5 

586 

246-2 

307-7 

556 

2329 

291-1 

525 

219-1 

273-8 

495 

205-7 

257-2 

585-5 

246 

307-5 

5558 

2328 

291 

524-7 

219 

273-7 

494-6 

205-6 

257 

585 

245-7 

307-2 

555 

232-4 

290-5 

524 

218-6 

273-3 

494 

205-3 

256-6 

584-6 

245-6 

307 

554 

232 

290 

523-4 

218-4 

273 

493-2 

205 

256-2 

584 

245-3 

306-6 

553 

231-5 

289-4 

523 

218-2 

272-7 

493 

204-9 

256-1 

583-2 

245 

306-2 

5522 

231-2 

289 

522-5 

218 

272-5 

492-8 

204-8 

256 

583 

244-9 

306-1 

552 

231-1 

288-8 

522 

217-7 

272-2 

492 

204-4 

255-5 

582-8 

244-8 

306 

651-7 

231 

288-7 

521  6 

217-6 

272 

491 

204 

255 

582 

244-4 

305-5 

551 

230-6 

288-3 

521 

217-3 

271-6 

490 

2035 

254-4 

581 

244 

305 

550-4 

230-4 

288 

520-2 

217 

271-2 

489-2 

203-2 

254 

580 

243-5 

304-4 

550 

2302 

287-7 

520 

216-9 

271-1 

489 

203-1 

253-8 

579-2 

243-2 

304 

549-5 

230 

287-5 

519-8 

216-8 

271 

488-7 

203 

253-7 

579 

243-1 

303-8 

549 

229-7 

287-2 

519 

216-4 

270-5 

488 

202-6 

253-3 

578-7 

243 

303-7 

548-6 

229-6 

287 

518 

216 

270 

487-4 

202-4 

253 

578 

242-6 

303-3 

548 

229-3 

286-6 

517 

215-5 

269-4 

487 

202-2 

252-7 

577-4 

242-4 

303 

547-2 

229 

286-2 

516-2 

215-2 

269 

486-5 

202 

252-5 

577 

242-2 

302-7 

547 

2289 

286  1 

516 

215-1 

268-8 

486 

201-7 

252-2 

576-5 

242 

302-5 

546-8 

228-8 

286 

515-7 

215 

268-7 

485-6 

201-6 

252 

576 

241-7 

302-2 

546 

228-4 

2855 

515 

214-6 

268-3 

485 

201-3 

251-6 

575-6 

241-6 

302 

545 

228 

285 

514-4 

214-4 

268 

484-2 

201 

251-2 

575 

241-3 

301-6 

544 

227-5 

284-4 

514 

214-2 

267-7 

484 

200-9 

251-1 

574-2 

241 

301-2 

543-2 

227-2 

284 

513  5 

214 

267-5 

483-8 

200-8 

251 

574 

240-9 

301-1 

543 

227-1 

283-8 

513 

213-7 

267-2 

483 

200-4 

250-5 

573-8 

2408 

301 

542-7 

227 

283-7 

512-6 

213-6 

267 

482 

200 

250 

573 

2404 

300-5 

542 

2266 

283-3 

512 

213-3 

266-6 

481 

199-5 

249-4 

572 

240 

300 

541-4 

226-4 

283 

511-2 

213 

266-2 

480-2 

199-2 

249 

571 

239-5 

299-4 

541 

226-2 

282-7 

511 

212-9 

266-1 

480 

199-1 

248-8 

570-2 

2392 

299 

5405 

226 

282-5 

I510-8 

2128 

266 

479-7 

199 

248-7 

570 

239-1 

298-8 

540 

2257 

282-2 

^510 

212-4 

265-5 

479 

198-6 

248-3 

569-7 

239 

298-7 

539-6 

2256 

282 

|509 

212 

265 

478-4 

198-4 

248 

214 


THERMOMETRICAL   EQUIVALENTS. 


S  -: 

13 

3 

H 

o  & 

s, 

p 

Reaumur. 

11 

o  S> 

L 

-G    « 

£x 

Reaumur. 

11 

O  be 

Fahren- 
heit. 

Reaumur. 

•A  » 

II 

478 

198-2 

247-7 

448-2 

185 

231-2 

418 

171-5 

214-4 

388-4 

158-4 

198 

477-5 

198 

2475 

448 

184-9 

231-1 

417-2 

171-2 

214 

388 

158-2 

197-7 

477 

197-7 

247-2 

447-8 

184-8 

231 

417 

171-1 

213-8 

387-5 

158 

197-5 

476-6 

1976 

247 

447 

184-4 

230-5 

416-7 

171 

213-7 

387 

157-7 

197-2 

476 

197-3 

246-6 

446 

184 

230 

416 

170-6 

213-3 

386-6 

157-6 

197 

4752 

197 

2462 

445 

183-5 

229-4 

4154 

170-4 

213 

386 

157-3 

196-6 

475 

1969 

246-1 

444-2 

183-2 

229 

415 

170-2 

212-7 

385-2 

157 

196-2 

474-8 

1968 

246 

444 

183-1 

228-8 

414-5 

170 

212-5 

385 

1569 

196-1 

474 

196-4 

245-5 

443-7 

183 

228-7 

414 

169-7 

212-2 

384-8 

156-8 

196 

473 

196 

245 

443 

182-6 

228-3 

4136 

169-6 

212 

384 

156-4 

195-5 

472 

195-5 

244-4 

442-4 

182-4 

228 

413 

169-3 

211-6 

383 

156 

195 

471-2 

195-2 

244 

442 

182-2 

227-7 

412-2 

169 

211-2 

382 

155-5 

194-4 

471 

195-1 

243-8 

441-5 

182 

227-5 

412 

168-9 

211-1 

381-2 

155-2 

194 

470-7 

195 

243-7 

441 

181-7 

227-2 

411-8 

168-8 

211 

381 

155-1 

193-8 

470 

194-6 

243-3 

440-6 

181-6 

227 

411 

168-4 

210-5 

380-7 

155 

193-7 

469-4 

194-4 

243 

440 

181-3 

226-6 

410 

168 

210 

380 

154-6 

193-3 

469 

194-2 

242-7 

439-2 

181 

2262 

409 

167-5 

209-4 

379-4 

154-4 

193 

468-5 

194 

242-5 

439 

180-9 

226-1 

408-2 

167-2 

209 

379 

154-2 

192-7 

468 

193-7 

242-2 

438-8 

180-8 

226 

408 

167-1 

208-8 

378-5 

154 

192-5 

467-6 

193-6 

242 

438 

1804 

225-5 

407-7 

167 

2087 

378 

153-7 

192-2 

467 

193-3 

241-6 

437 

180 

225 

407 

166-6 

208-3 

377-6 

153-6 

192 

466-2 

193 

241-2 

436 

179-5 

224-4 

406-4 

166-4 

208 

377 

1533 

191-6 

466 

192-9 

241-1 

435-2 

1792 

224 

406 

166-2 

207-7 

376-2 

153 

191-2 

465-8 

192-8 

241 

435 

179-1 

223-8 

405-5 

166 

207-5 

376 

1529 

191-1 

465 

192-4 

240-5 

434-7 

179 

223-7 

405 

1657 

207  2 

375-8 

152-8 

191 

464 

192 

240 

434 

178-6 

223-3 

4046 

1656 

207 

375 

152-4 

190-5 

463  • 

191-5 

239-4 

433-4 

178-4 

223 

404 

165-3 

206-6 

374 

152 

190 

462-2 

191-2 

239 

433 

178-2 

222-7 

403-2 

165 

2062 

373 

151  5 

189-4 

462 

191-1 

238-8 

432-5 

178 

222-5 

403 

164-9 

206-1 

372-2 

151-2 

189 

461-7 

191 

238-7 

432 

177-7 

222-2 

402-8 

164-8 

206 

372 

151-1 

188-8 

461 

190-6 

2383 

431-6 

177-6 

222 

402 

164-4 

205-5 

371-7 

151 

188-7* 

460-4 

190-4 

238 

431 

177-3 

221  6 

401 

164 

205 

371 

150-6 

188-3 

460 

190-2 

237-7 

430-2 

177 

221-2 

400 

163-5 

204-4 

370-4 

150-4 

188 

459-5 

190 

237-5 

430 

1769 

221-1 

399-2 

163-2 

204 

370 

1  50-2 

187-7 

459 

189-7 

237-2 

429-8 

1768 

221 

399 

163-1 

203-8 

3695 

150 

187-5 

4586 

189-6 

237 

429 

176-4 

220  5 

398-7 

163 

203  7 

369 

1497 

187-2 

458 

189-3 

236-6 

428 

176 

220 

398 

162-6 

2033 

368-6 

149-6 

187 

457-2 

189 

2362 

427 

1755 

219-4 

397-4 

162-4 

203 

368 

149-3 

1866 

457 

188-9 

236-1 

426-2 

175-2 

219 

397 

1622 

202-7 

367-2 

149 

186-2 

4568 

88-8 

236 

426 

1751 

218-8 

396-5 

162 

202-5 

367 

148-9 

186-1 

456 

88-4 

235-5 

4257 

175 

218-7 

396 

161-7 

202-2 

3668 

148-8 

186 

455 

88 

235 

425 

174-6 

218-3 

3956 

161  6 

202 

366 

148-4 

185-5 

454 

87-5 

234-4 

424-4 

174-4 

218 

395 

161  3 

201-6 

365 

148 

185 

453-2 

87-2 

234 

424 

174-2 

217-7 

394-2 

161 

201-2 

364 

147-5 

184-4 

453 

87-1 

233-8 

423-5 

174 

217-5 

394 

160-9 

201-1 

3632 

147-2 

184 

452-7 

87 

233-7 

423 

173-7 

217-2 

393-8 

160-8 

201 

363 

147-1 

183-8 

452 

86-6 

2333 

422-6 

173  6 

217 

393 

1604 

2005 

362-7 

147 

183-7 

451-4 

86-4 

233 

422 

173-3 

2166 

392 

160 

200 

362 

1466 

183-3 

451 

86-2 

232-7 

421-2 

173 

216-2 

391 

159-5 

99-4 

361-4 

146-4 

183 

450-5 

86 

232-5 

421 

172-9 

216-1 

390-2 

159-2 

99 

361 

146-2 

182-7 

450 

857 

32-2 

420-8 

172-8  216 

390 

59-1 

988 

360-5 

146 

182-5 

449-6 

856 

232 

420 

172-4 

215-5 

389-7 

159 

98-7 

360 

1457 

182-2 

449 

85-3 

231-6 

419 

72 

215 

389 

1586 

198-3 

3596 

145-6 

182 

THERMOMETRICAL  EQUIVALENTS. 


215 


fa 

p 

Reaumur. 

"I* 

Sg 

U  so 

P 

Reaumur. 

.±  «5 

11 

A 

u  S 
11 

M 

Reaumur. 

11 

0  u 

t.2 

I1 

Reaumur. 

11 

0  tt> 

359 

1453 

181  6 

329 

132 

165 

299 

118-6 

148-3 

269-6 

105-6 

132 

358-2 

145 

181-2 

328 

131-5 

164-4 

298-4 

118-4 

148 

269 

1053 

131-6 

358 

144-9 

181-1 

327-2 

131-2 

164 

298 

1182 

147-7 

268-2 

105 

131-2 

3578 

144-8 

181 

327 

131  1 

163-9 

297-5 

118 

147-5 

268 

104  8 

131-1 

357 

144-4 

180-5 

326-7 

131 

163-7 

297 

117-7 

1472 

267-8 

104-8 

131 

356 

144 

180 

326 

130-6 

163-3 

2966 

1176 

147 

267 

104-4 

130-5 

355 

143-5 

1794 

325-4 

130-4 

163 

296 

117-3 

1466 

266 

104 

130 

354-2 

143-2 

179 

325 

130-2 

162-7 

295-2 

117 

1462 

265 

103  5 

129-4 

354 

143  1 

178-8 

324-5 

130 

162-5 

295 

1169 

146-1 

264-2 

1032 

129 

353-7 

143 

1787 

324 

129-7 

162-2 

2948 

1168 

146 

264 

103-1 

128-9 

353 

142  6 

178-3 

323-6 

129-6 

162 

294 

116-4 

145-5 

263-7 

103 

128-7 

352-4 

142-4 

178 

323 

129-3 

161-6 

293 

116 

145 

263 

102-6 

1283 

352 

1422 

177-7 

322-2 

129 

161  2 

292 

115-5 

144-4 

262-4 

102-4 

128 

351-5 

142 

177-5 

322 

1288 

161-1 

291  2 

1152 

144 

262 

102-2 

127-7 

351 

141  8 

177-2 

321-8 

1288 

161 

291 

115-1 

143-8 

261-5 

102 

127  5 

350-6 

141-6 

177 

321 

128-4 

1605 

290-7 

115 

1437 

261 

101-7 

127-2 

350 

141-3 

176-6 

320 

128 

160 

290 

1146 

143-3 

260-6 

101-6 

127 

349-21141 

176-2 

319 

127-5 

159-4 

289-4 

1144 

143 

260 

101-3 

1266 

349 

140-9 

176-1 

^18-2 

127-2 

159 

289 

1142 

1427 

259-2 

101 

1262 

348-8 

140-8 

176 

318 

127-1 

158-8 

288-5 

114 

142-5 

259 

100-8 

126-1 

348 

1404 

175-5 

317-7 

127 

158-7 

288 

113-7 

1422 

258-8 

1008 

126 

347 

140 

175 

317 

126-6 

1583 

287-6 

1136 

142 

258 

100-4 

125-5 

346 

139-5 

174-4 

316-4 

1264 

158 

287 

113-3 

141-6 

257 

100 

125 

3452 

1392 

174 

316 

1262 

1577 

286-2 

113 

141-2 

256 

99-5 

124-4 

345 

139  1 

173-8 

3155 

126 

157-5 

286 

1128 

141-1 

255-2 

99-2 

124 

344-7 

139 

173-7 

315 

125-7 

157-2 

2858 

1128 

141 

255 

99-1 

1238 

344 

138-6 

1733 

314-6 

125-6 

157 

285 

1124 

1405 

254-7 

99 

123-7 

3434 

1384 

173 

314 

125-3 

156-6 

284 

112 

140 

254 

98-6 

123-3 

343 

1382 

172-7 

3132 

125 

156-2 

283 

111-5 

1394 

2534 

98-4 

123 

342-5 

138 

172-5 

313 

1248 

156-1 

282-2 

111-2 

139 

253 

98-2 

122-7 

342 

137-7 

1722 

3128 

124-8 

156 

282 

111-1 

1389 

2525 

98 

122-5 

341  6 

137-6 

172 

3*12 

124  5 

155-5 

281-7 

111 

138-7 

252 

97-9 

122-2 

341 

137-3 

171-6 

311 

124 

155 

281 

110-6 

1383 

251-6 

97-6 

122 

340-2 

137 

171-2 

310 

123-5 

1544 

280-4 

110-4 

138 

251 

97-3 

121-6 

340 

1369 

171-1 

309-2 

1232 

154 

280 

110-2 

137-7 

250-2 

97 

121  2 

339-8 

1368 

171 

309 

123-1 

1538 

279-5 

110 

137-5 

250 

96-9 

121-1 

339 

136-4 

170-5 

3087 

123 

1537 

279 

1097 

137-2 

249-8 

968 

121 

338 

136 

170 

308 

1226 

153-3 

278-6 

109-6 

137 

249 

96-4 

120-5 

337 

1355 

169-4 

307-4 

122-4 

153 

278 

1093 

136-6 

248 

96 

120 

336-2 

135-2 

169 

307 

122  2 

152-7 

277-2 

109 

136-2 

247 

95  5 

119-4 

336 

135-1 

168-8 

306-5 

122 

152-5 

277 

108-8 

136-1 

246-2 

95-2 

119 

335-7 

135 

168-7 

306 

121-7 

152-2 

276-8 

108-8 

136 

246 

95  1 

118-9 

335 

134-6 

1683 

305-6 

121  6 

152 

276 

1084 

135-5 

2457 

95 

118-7 

334-4 

134-4 

168 

305 

121-3 

151-6 

275 

108 

135 

245 

946 

118-3 

334 

134-2 

167-7 

304-2 

121 

151  2 

274 

107-5 

134-4 

244-4 

94-4 

118 

333-5 

134 

167-5 

304 

120-9 

151-1 

2732 

1072 

134 

244 

94-2 

117-8 

333 

133-7 

1672 

3038 

1208 

151 

273 

107  1 

1338 

243-5 

94 

117-5 

332-6 

133-6 

167 

303 

120-4 

150-5 

2727 

107 

1337 

243 

938 

117-2 

332 

133-3 

1666 

302 

120 

150 

272 

106-6 

1333 

2426 

936 

117 

331-2 

133 

166-2 

301 

119-5 

149-4 

271-4 

106  4 

133 

242 

93-3 

1166 

331 

1329 

166-1 

300-2 

119-2 

149 

271 

1062 

132-7 

241-2 

93 

1162 

3308 

132-8 

166 

300 

119-1 

148:9 

2705 

106 

1325 

241 

92-9 

1161 

330 

132-4 

165-5 

2997 

119 

148-7 

270 

1057 

132-2 

2408 

92-8 

116 

216 


THBRMOMETRICAL  EQUIVALENTS. 


Fahren- 
heit. 

1 

II 

Fahren- 
heit. 

Reaumur. 

It 

1* 

Reaumur. 

1! 

o  &> 

Fahren- 
heit. 

Reaumur. 

it 

240 

924 

115-5 

209-7 

79 

987 

180 

657 

82-2 

1508 

52-8 

66 

239 

92 

115 

209 

78-6 

983 

1796 

65-6 

82 

150 

52-4 

65-5 

238 

915 

114-4 

208-4 

78-4 

98-0 

179 

653 

81-6 

149 

52 

65 

237-2 

912 

114 

208 

78-2 

978 

178-2 

65 

81-2 

148 

51-5 

64-4 

237 

91  1 

113-9 

207-5 

78 

975 

178 

64-9 

81-1 

147-2 

51-2 

64 

236-7 

91 

113-7 

207 

77-7 

97  2 

177-8 

64-8 

81 

147 

51-1 

63-9 

236 

903 

113-3, 

206-6 

77-6 

97 

177 

64-4 

80  5 

146-7 

51 

63-7 

235-4 

90-4 

113 

206 

77-3 

96-6 

176 

64 

80 

146 

506 

63-3 

235 

902 

112-7 

205-2 

77 

96  2 

175 

63-5 

79-4 

145-4 

50'4 

63 

234-5 

90 

112-5 

205 

76-9 

96-1 

174-2 

632 

79 

145 

50-2 

62-7 

234 

89-7 

1122 

2048 

768 

96 

174 

63-1 

788 

144-5 

50 

62-5 

2336 

896 

112 

204 

76-4 

95  5 

1737 

63 

78-7 

144 

497 

622 

233 

89-3 

111-6 

203 

76 

95 

173 

62-6 

78-3 

143-6 

496 

62 

2322 

89 

111-2 

202 

75-5 

94-4 

172-4 

62-4 

78 

143 

493 

61-6 

232 

88-9 

nri 

201-2 

75-2 

94 

172 

62-2 

77-7 

142-2 

49 

61-2 

2318 

88-8 

111 

201 

75-1 

93-9 

171-5 

62 

77-5 

142 

48-9 

61-1 

231 

88-4 

110-5 

200-7 

75 

93-7 

171 

61-7 

77-2 

141-8 

488 

61 

230 

88 

110 

200 

74-6 

93-3 

170-6 

61-6 

77 

141 

48-4 

60-5 

229 

87-5 

109-4 

199-4 

74-4 

93 

170 

613 

76-6 

140 

48 

60 

228-2 

87-2 

109 

199 

74-2 

927 

169  2 

61 

762 

139 

47  5 

59-4 

228 

87-1 

108-9 

198-5 

74 

92-5 

169 

60-8 

76-1 

1382 

47-2 

59 

2277 

87 

108-7 

198 

737 

922 

168-8 

60-8 

76 

138 

47-1 

58-8 

227 

86-6 

1083 

197-6 

73-6 

92 

168 

604 

75-5 

137-7 

47 

58-7 

2264 

86-4 

108 

197 

73-3 

91  6 

167 

60 

75 

137 

46-6 

58-3 

226 

86-2 

107-8 

196-2 

73 

91-2 

166 

595 

74-4 

136-4 

46-4 

58 

225-5 

86 

107-5 

196 

72-8 

91-1 

165-2 

59-2 

74 

136 

46-2 

57-7 

225 

85-7 

107-2 

195-8 

72-8 

91 

165 

59-1 

739 

135-5 

46 

57-5 

224-6 

85-6 

107 

195 

72-4 

90-5 

164-7 

59 

73-7 

135 

45-8 

57-2 

224 

85-3 

106-6 

194 

72 

90 

164 

586 

73-3 

134-6 

45  6 

57 

223-2 

85 

1062 

193 

71-5 

89-4 

163-4 

58-4 

73 

134 

45-3 

56-6 

223 

84-9 

106-1 

192-2 

71  2 

89 

163 

58-2 

72-7 

133-2 

45 

56-2 

2228 

84-8 

106 

192 

71-1 

88-8 

162  5 

58 

72-5 

133 

44-9 

56-1 

222 

84-4 

105-5 

191-7 

71 

88-7 

162 

577 

72-2 

132-8 

44-8 

56 

221 

84 

105 

191 

70-6 

88  3 

161  6 

57-6 

72 

132 

44-5 

55-5 

220 

83-5 

104-4 

190-4 

704 

88 

161 

57-3 

71-6 

131 

44 

55 

219-2 

83-2 

104 

190 

70-2 

878 

160-2 

57 

71-2 

130 

435 

54-4 

219 

83  1 

103  9 

189-5 

70 

87  5 

160 

56-8 

71-1 

129-2 

43-2 

54 

218-7 

83 

103-7 

189 

69-7 

87-2 

159-8 

56-8 

71 

129 

43-1 

53-9 

218 

826 

103-3 

188-6 

69-6 

87 

159 

564 

70-5 

128-7 

43 

53-7 

217-4 

82-4 

103 

188 

69-3 

86-6 

158 

56 

70 

128 

426 

53-3 

217 

82-2 

102-7 

187-2 

69 

86-2 

157 

55-5 

69-4 

127-4 

42-4 

53 

216-5 

82 

102-5 

187 

68-9 

86-1 

1562 

55-2 

69 

127 

422 

52-7 

216 

8T7 

102-2 

1868 

68-8 

86 

156 

55  1 

68-9 

126-5 

42 

52-5 

2156 

81-6 

102 

186 

68-4 

85-5 

155-7 

55 

68-7 

126 

41-8 

522 

215 

81-3 

1016 

185 

68 

85 

155 

546 

68-3 

1256 

41  6 

52 

214-2 

81 

10T2 

184 

67-5 

84-4 

154-4 

544 

68 

125 

41  3 

51-6 

214 

80-9 

101-1 

183-2 

67.2 

84 

154 

54-2 

67-7 

1242 

41 

51-2 

2138 

80-8 

101 

183 

67-1 

839 

153-5 

54 

67-5 

124 

40-9 

51-1 

213 

80-4 

100-5 

182-7 

67 

83-7 

153 

53-7 

67-2 

1238 

40-8 

51 

212 

80 

100 

182 

66-6 

83-3 

152-6 

53-6 

67 

123 

40-4 

50-5 

211 

79-5 

99-4 

181-4 

66-4 

83 

152 

53-3 

666 

122 

40 

50 

210-2 

79-2 

99 

181 

66-2 

82-7 

151.2 

53 

66-2 

121 

39-5 

49-4 

210 

79-1 

98-9 

180-5 

66 

825 

151 

529 

66-1 

120-2 

39-2 

49 

THERMOMETRICAL    EQUIVALENTS. 


217 


Reaumur. 

ii 

u  & 

Si 

fa 

Reaumur. 

ll 

k 
jP 

Reaumur; 

ii 

Fahren- 
heit. 

Reaumur. 

i| 

s£ 

39-1 

48-9 

90-5 

26 

32-5 

61 

129 

16  1 

302 

—0-8 

i 

39 

48-7 

90 

25-7 

32-2 

60-8 

128 

16 

30 

—0-9 

—1-1 

38-6 

48-3 

896 

25-6 

32 

60 

12-4 

15-5 

29-7 

—  1 

—12 

38-4 

48 

89 

253 

31  6 

59 

12 

.  15 

29 

—1-3 

—  1-6 

38-2 

47-7 

88-2 

25 

31-2 

58 

11-5 

14-4 

28-4 

—  1-6 

—2 

38 

47-5 

88 

24-9 

31-1 

57-2 

11-2 

14 

28 

—  1-7 

—2-2 

37-7 

47-2 

87-8 

24-8 

31 

57 

11-1 

138 

27-5 

—2 

—2-5 

37  6 

47 

87 

244 

305 

56-7 

11 

13-7 

27 

—2-2 

—2-7 

37-3 

46-6 

86 

24 

30 

56 

106 

133 

26-6 

—2-4 

—3 

37 

46-2 

85 

23-5 

294 

554 

10-4 

13 

26 

—26 

—3-3 

36-9 

46-1 

84-2 

232 

29 

55 

102 

12'7 

25-2 

—3 

—3-7 

36-8 

46 

84 

23-1 

28-9 

54-5 

10 

12-5 

25 

—3-1 

—3-8 

36'4 

45-5 

83-7 

23 

287 

54 

9-7 

122 

24-8 

—32 

—4 

36 

45 

83 

22-6 

28-3 

53-6 

9-6 

12 

24 

—35 

—4-4 

355 

44-4 

82-4 

22-4 

28 

53    . 

9-3 

11-6 

23 

—4 

—5 

35-2 

44 

82 

222 

277 

52-2 

9 

11-2 

22 

—4-4 

—5-5 

35-1 

43-9 

81-5 

22 

27  5 

52 

89 

11-1 

21-2 

—4-8 

—6 

35 

43-7 

81 

21-7 

272 

51-8 

8-8 

11 

21 

—4-9 

—6-1 

34-6 

433 

80-6 

216 

27 

51 

8-4 

10-5 

20-7 

—5 

—6'2 

34-4 

43 

80 

21-3 

26-6 

50 

8 

10 

20 

—5-3 

—6-6 

34-2 

427 

792 

21 

262 

49 

75 

9-4 

19-4 

—56 

—7 

34 

42-5 

79 

20-9 

26-1 

48-2 

7-2 

9 

19 

—5-7 

—7-2 

33-8 

42-2 

78-8 

20-8 

26 

48 

7-1 

89 

18-5 

—6 

—7-5 

33-6 

42 

78 

20-4 

25-5 

47-7 

7 

8-7 

18 

—62 

—7-7 

33-3 

41  6 

77 

20 

25 

47 

66 

8-3 

17-6 

—6-4 

—8 

33 

41-2 

76 

19-5 

24-4 

46-4 

6-4 

8 

17 

—6-6 

—8-3 

32-9 

41-1 

75-2 

19-2 

24 

46 

6-2 

7-7 

16-2 

—7 

—8-7 

328 

41 

75 

19-1 

23-8 

45-5 

6 

7-5 

16 

—7-1 

—89 

32'4 

40-5 

?74-7 

19 

23-7 

45 

57 

7-2 

158 

—7-2 

—9 

32 

40 

74 

18-6 

233 

44-6 

57 

7  • 

15 

—75 

—94 

31-5 

39-4 

73-4 

18-4 

23 

44 

53 

66 

14 

—8 

—10 

31-2 

39 

73 

18-2 

22-7 

43-2 

5 

62 

13 

—8-4 

—10-5 

3T1 

38-9 

72-5 

18 

22-5 

43 

4-9 

6-1 

12-2 

—8-8 

—11 

31 

38-7 

72 

17-7 

22-2 

428 

4-8 

6 

12 

—8.9 

—  11  1 

30'6 

38'3 

71-6 

176 

22 

42 

4-4 

5-5 

11-7 

—  9 

—11-2 

30-4 

38 

71 

17-3 

216 

41 

4 

5 

11 

—9-3 

—11  6 

30'2l  37-7 

70-2 

17 

21-2 

40 

35 

44 

10-4 

—9-6 

—  12 

30 

37-5 

70 

169 

21-1 

39-2 

3-2 

4 

10 

—9-7 

—  12-2 

29-7 

372 

69-8 

168 

21 

39 

3-1 

39 

9-5 

—10 

—125 

29-6 

37 

69 

16-4 

20-5 

38-7 

3 

3-7 

9 

—  10-2 

—12-7 

29  3 

36-6 

68 

16 

20 

38 

2-6 

33 

86 

—104 

—  13 

29 

36-2 

67 

15'5 

19-4 

.37-4 

2-4 

3 

8 

—  10-6 

—  133 

28-9 

36  1 

66-2 

15-2 

19 

37 

2-2 

'2-7 

7-2 

—  11 

—13-7 

28-8 

36 

66 

15-1 

18-8 

36-5 

2 

2-5 

7 

—11-1 

—13-9 

28-4 

35-5 

65-7 

15 

187 

36 

1-7 

2-2 

6-8 

—11-2 

—14 

28 

35 

65 

14-6 

18-3 

35-6 

1-6 

2 

6 

—11-5 

—  14-4 

27-5 

34-4 

64-4 

14-4 

18 

35 

13 

16 

5 

—  12 

—15 

272 

34 

64 

14-2 

17-7 

34-2 

1 

1-2 

4 

—  12-4 

—15-5 

27-1 

339 

63  5 

14 

17-5 

34 

0-9 

ri 

32 

—128 

—16 

27 

337 

63 

13-7 

17-2 

33-8 

0-8 

1 

3 

—12-9 

—161 

26-6 

333 

62-6 

136 

17 

33 

0-4 

0-5 

2-7 

—13 

—16-2 

26-4 

33 

62 

13-3 

166 

32 

0 

0 

2 

—133 

—16-6 

26-2 

327 

6T2 

13 

16-2 

31 

—0-4 

—0-5 

1-4 

—  13-6 

—17 

218 


SOURCES   AND   MANAGEMENT   OF   HEAT. 


Fahren- 
heit. 

Reaumur. 

.i  « 

11 

O  ti) 

a  . 

"  ~ 

ij 

Reaumur. 

1! 

O  SD 

Fahren- 
heit. 

Reaumur. 

11 

O  bo 

d    . 

J=  "*> 
«T 

Reaumur. 

•3«j 

SI 

1 

—  13-7 

—  17-2 

—  9-4 

—  18-4 

—23 

—20 

—23-1 

—28-9 

—30 

—27-5 

—344 

05 

—14 

—  17-5 

—  10 

—  18-6 

—23-3 

—20-2 

—232 

—29 

—31 

—28 

—35 

0 

—  14-2 

—17-7 

—  10-7 

—19 

—23-7 

—21 

—23-5 

—29-4 

—32 

—28-4 

-35-5 

—0-4 

—14-4 

—18 

—11 

-19-1 

—23-8 

—22 

—24 

—30 

—  32-8 

—28-8 

—36 

—  1 

—  146 

—  18-3 

—  11-2 

—19-2 

—  24 

—23 

—24-4 

—30-5 

—33 

—28-9 

—36-1 

—1-7 

—  15 

—18-7 

—  12 

—195 

—24-4 

—23-8 

—248 

—31 

—33-2 

—29 

—36-2 

—2 

—  15  1 

—  18-9 

—13 

—20 

—25 

—24 

—24-9 

—31-1 

—34 

—29-3 

—366 

—2-2 

—  15-2 

—  19 

—14 

—20-4 

—25-5 

—24-2 

—25 

—31-2 

—34-6 

—29-6 

—37 

—3 

—  155 

—194 

—  14-8 

—208 

—26 

—25 

—253 

—31-6 

—35 

—29-7 

—37-2 

—4 

—16 

—20 

—15 

—209 

—261 

—256 

—256 

—32 

—355 

—30 

—37-5 

—  5 

—164 

—205 

—  15-2 

—21 

-26-2 

—26 

—25-7 

—322 

—36 

—302 

—37-7 

—5-8 

—  16-8 

—21 

—16 

—21-3 

—26-6 

—26-5 

—26 

—32-5 

—36-4 

—30-4 

—38 

—6 

—168 

—21  1 

—  16-6 

—21-6 

—27 

—27 

—262 

—32-7 

—37 

—30-6 

—38'3 

—6-2 

—17 

—21-2 

—  17 

—21-7 

—27-2 

—274 

—  26-4 

—33 

—37-7 

—31 

—38-7 

—  7 

—17-3 

—21-6 

—17-5 

—22 

—27-5 

—28 

—266 

—33-3 

—38 

—31-1 

—38-9 

—7-6 

—17-6 

—22 

—18 

—22-2 

—27-7 

—28-7 

—27 

—33-7 

—38-2 

—31-2 

—39 

—8 

—  17-7 

—22-2 

—  184 

—22-4 

—28 

—29 

-27-1 

—338 

—39 

—31  5 

—39-4 

—8-5 

—18 

—22-5 

—19 

—226 

—28-3 

—29-2 

—27-2 

—34 

—40 

—32 

—40 

—9 

—182 

—22-7 

—19-7 

—23 

—28-7 

CHAPTER  XL 


SOURCES  AND   MANAGEMENT   OP   HEAT. 

HEAT  plays  an  important  part  in  changing  the  state  and  pro- 
perties of  bodies,  and  we,  therefore,  devote  a  chapter  to  the 
various  modes  of  applying  that  agent  in  chemical  operations. 
The  processes  dependent  upon  its  action  are,  principally,  FUSION, 
IGNITION,  CALCINATION,  INCINERATION,  ROASTING,  DEFLAGRA- 
TION, REDUCTION,  CUPELLATION,  SUBLIMATION,  DISTILLATION, 
DIGESTION,  DECOCTION,  BOILING,  SOLUTION,  EVAPORATION, 
CRYSTALLIZATION,  and  DESICCATION. 

FURNACES. — Laboratory  furnaces  differ  in  construction  accord- 
ing to  the  uses  for  which  they  are  designed.  The  main  parts  of 
every  furnace  are  the  body  in  which  the  heat  is  produced,  the 
grate  or  bars  upon  which  the  fuel  rests,  the  ash  pan  for  receiving 
the  residue,  and  smoke-pipe  for  conducting  off  the  gaseous  pro- 
ducts of  combustion. 

Most  laboratories  at  the  present  day  have  a  stationary  wind  or 


FURNACES. 


219 


air  furnace  set  in  brickwork.  Being  applicable  only  for  crucible 
operations,  its  usefulness  is  limited.  In  private  experimental 
laboratories,  the  gas  sand-bath,  explained  at  p.  66,  and  one  of 
the  portable  furnaces  about  to  be  mentioned,  would  be  far  more 
efficient  and  convenient.  The  object  should  be  to  select  such  an 
arrangement  as  will  admit  of  the  greatest  extent  of  application, 
and,  therefore,  a  public  institution  with  the  jack,  Fig.  14,  will 
only  need,  besides,  a  Barren's  table,  a  small  charcoal  furnace,  and 
the  usual  gas  lamps,  to  be  amply  provided  for  the  accomplish- 
ment of  any  furnace  experiments.  Still,  for  the  sake  of  giving 
completeness  to  our  work,  we  proceed  to  describe  the  common 
form  of  a, — 

Wind  Furnace. — This  is  a  close  furnace,  in  which  the  draught 
of  the  chimney  urges  the  fire,  instead  of  a  bellows,  as  in  blast 
furnaces.  Fig.  123  shows  a  vertical  section.  The  body  A,  may 

Fig.  123. 


have  its  interior  square  or  circular,  though  the  latter  form  is 
most  convenient  and  economical  for  fuel,  and  should  abut  against 
a  high  chimney.  The  ash-pit  B  is  separated  from  the  body  of 
the  furnace  by  movable,  cast-iron,  bars,  which  form  a  support  for 


220 


FURNACES. 


Fig.  124. 


the  fire-brick  on  which  the  crucibles  rest,  as  well  as  for  the  coal 
used  in  heating  them.  The  lateral  flue,  connecting  with  the 
chimney  C,  should  be  short  and  contracted  at  the  throat,  so  as 
to  promote  the  perfect  combustion  of  the  gases  before  they  pass 
off,  and  thus  economize  heat  as  well  as  increase  the  draught.  It 
must  also  be  fitted  with  a  damper.  All  the  interior  of  the  fur- 
nace must  be  lined  with  tile  or  brick  made  of  refractory  clay ; 
and  the  ash-pit  should  have  tubes  leading  from  the  outside  of  the 
apartment,  for  supplying  currents  of  air  to  the  burning  fire,  and 
augmenting  the  heat.  The  mouth  of  the  furnace,  which  is  the 
opening  for  the  introduction  of  fuel  and  the  crucibles,  may  be  a 
sliding  door  of  cast-iron,  lined  internally  with  a  soap-stone  slab, 
as  a  protection  against  the  fire,  as  shown  at 
a,  or  it  may  be  hung  to  the  chimney  wall  by 
chains  working  on  pulleys,  so  as  to  move  ver- 
tically instead  of  horizontally.  An  opening 
in  the  centre,  fitted  with  a  soap-stone  plug, 
serves  for  observing  the  progress  of  the  ope- 
ration as  may  be  desirable.  The  cast-iron 
hood  D,  over  the  furnace,  is  to  avert  the  pro- 
gress of  uprising  sparks,  dust,  &c.,  and  carry 
them  off,  through  a  valve,  into  the  chimney.  The  dimensions  of 
the  pot  may  be  10-12  inches  diameter,  and  20-24  inches  height 

from  the   grate-bars  up- 

Fig.125.  Fig.  126.  wardg<        The    grate.barg 

should  be  set  three-fourth 
inches  apart ;  and  the 
chimney-flue  should  run 
to  a  height  of  about  30 
feet. 

It  is  useless  to  multiply 
furnaces  in  a  small  labo- 
ratory, for  they  occupy 
room  which  may  be  want- 
ing for  other  purposes,  and,  therefore,  a  selection  should  be  made 
of  one  which  in  its  arrangement  is  applicable  to  all  the  necessities 
of  the  chemist.  One  of  either,  with  a  small  charcoal  furnace, 
Fig.  124,  such  as  may  be  bought  at  any  crockery  shop,  for  table 
use,  will  comprise  all  that  is  required  of  this  sort  of  apparatus. 


LUHME'S  UNIVERSAL  FURNACE. 


221 


Universal  Furnace. — Figs.  125,  126,  exhibit  this  furnace,  the 
cylindrical  form  of  which  is  to  be  preferred  on  account  of  its 
producing  a  higher  heat  with  less  fuel  than  any  other.  It  is  of 
strong  plate-iron,  and  lined  in  the  body  and  dome  with  refractory 
fire-clay.  Its  dimensions  are  twenty-four  inches  in  height,  and 
nine  inches  in  diameter.  The  body,  «,  £>,  e,  d,  is  capped  with  a 
ring  of  the  same  circumference  as  the  clay  cylinder  beneath. 
The  doors  are  shown  at  g  and  h.  The  circular  openings,  #,  x, 
opposite  to  each  other,  are  for  the  passage  of  tubes,  and  when 
out  of  use  can  be  closed  by  the  plugs  accompanying  the  furnace 
for  that  purpose.  The  interior  of  the  furnace,  as  seen  from  above, 
is  shown  by  Fig.  127.  The  knobs,  e,  e,  e,  projecting  inwardly, 
serve  as  supports  for  vessels  which  are  smaller  than  the  mouth  of 


Fig.  127. 


Fig.  128. 


Fig.  129. 


the  furnace,  whilst  the  iron  juts,  d,  d,  c?,  directed  outwardly,  are 
rests  for  the  larger,*  this  arrangement  being  necessary,  in  both  in- 
stances, to  the  perfection  of  the  draught.  The  iron  jacket,  Fig. 
128,  adapted  to  the  opening,  a  d,  Fig.  125,  forms  a  support  for 


Fig.  130. 


Fig.  131. 


the  double  sand-bath,   Fig.  129,   for  retorts,  and  other  glass 
vessels.     The  slope  on  the  side  of  the  sand-bath  is  for  the  exit  of 


222 


KENT  S   UNIVERSAL  FURNACE. 


the  neck  of  the  retort ;  and  the  circular  openings,  k,  k,  7c,  &,  Fig. 
130,  are  fitted  with  covers,  by  which  to  augment  or  decrease  the 
draught,  as  may  be  required. 

A  supplementary  sand-bath,  Fig.  131,  is  made  with  a  broad 
extent  of  surface  for  digestions,  evaporations,  &c. 

The  dome,  Fig.  132,  confers  the  powers  of  a  wind  furnace 
when  high  heat  is  required.  As  this  chimney  becomes  too  hot  to 
be  handled,  it  is  removed  when  heated  with  suitable  tongs,  the 
form  of  which  is  shown  in  Fig.  133. 

Kent's  universal  furnace,  which  is  an  improvement  upon  the 
above,  is  shown  by  Fig.  134.  The  body  is  fourteen  inches  high, 
by  seven  inches  in  diameter,  and  in  material  and  general  con- 
struction is  similar  to  the  one  just  described.  There  are  six 
doors : — one  at  the  base  for  the  admission  of  air,  another  in  the 
middle  for  the  entrance  of  the  fuel  and  for  the  reception  of  the 
muffle  used  in  cupellation.  The  door  in  the  dome  is  for  the  pur- 
pose of  feeding  the  fire  in  crucible  operations ;  and  that  in  the 


Fig.  132. 


Fig.  134. 


Fig.  133. 


side,  at  the  top,  for  the  reception  of  the  neck  of  a  retort,  or  of  a 
sand-bath.      There  are  two  lateral  openings,  opposite  to  each 


EVAPORATING  AND   REVERBERATORY  FURNACES.  223 

other,  for  the  passage  of  tubes,  or  of  an  iron  bar  as  a  support  to 
the  rear  end  of  a  muffle. 

The  two  circular  openings,  by  which  it  is  coupled  with  the  pipes 
connecting  it  with  the  laboratory  flue,  are  closed  by  movable 
plugs.  In  crucible  operations,  the  smoke-pipe  should  lead  from 
the  top  opening,  and  in  evaporations,  from  the  aperture  in  the 
back.  The  openings  in  the  flue  must  be  above  the  level  of  the 
furnace. 

An  opening  at  the  base  is  for  the  introduction  of  the  mouth  of 
a  bellows,  by  which  it  may  be  converted  into  a  blast  furnace. 
This  implement  may  be  used  in  the  following  manner : 

1.  As  an  evaporating  and  calcining  furnace. — As  very  high 
heat  is  seldom  required  for  evaporations,  the  body  of  the  furnace 
alone  answers  every  purpose.     For  small  operations,  or  when  but 
a  small  fire  is  required,  its  capacity  may  be  diminished  by  in- 
serting  an   inner   cylinder   of  baked   clay.      To   increase   the 
draught,  all  the  doors  should  be  closed,  and  to  augment  still 
further  the  heat,  as  is  necessary  in  the  calcination  of  certain  sub- 
stances, the  dome  and  chimney  may  be  used.   In  this  latter  case, 
by  means  of  the  door  in  the  middle,  the  progress  of  the  operation 
may  be  examined  without  removing  the  chimney  dome,  or  cooling 
the  interior  of  the  furnace. 

The  sand  and  other  baths,  which  have  their  places  upon  the 
top  of  this  furnace;  serve  for  digestions,  evaporations,  &c.,  in 
vessels  which  require  the  abatement  and  equalization  of  the  heat 
by  intermedia. 

2.  As   a  reverberator^/  furnace. — This   kind   of  furnace   is 
adapted  to  operations  demanding  a  high  temperature,  as  in  the 
heating  of  crucibles,  tubes,  &c.,  and  also  in  sublimation  and  simi- 
lar processes  requiring  the  application  of  a  steady  heat  to  all 
portions  of  the  vessel,  rather  than  a  very  great  heat  to  any  one 
part  of  it. 

The  furnace  is  rendered  reverberatory  by  the  use  of  the  dome, 
which  allows  the  vessel  to  be  entirely  surrounded  by  flame,  and 
reflects  back  the  heat  upon  and  around  its  whole  surface,  and 
thus  by  equalizing  the  temperature,  prevents  the  condensation  of 
vapors  in  the  upper  parts, — an  important  object  in  distilling  from 
beaked  vessels. 

Coke  or  charcoal  is  the  fuel  generally  used,  the  latter  being  pre- 


224  WIND  AND  BLAST  FURNACES. 

ferable  for  a  furnace  of  small  dimensions ;  and  the  draught  may 
be  increased  by  lengthening  the  chimney. 

The  crucible,  or  vessel,  must  be  placed  in  the  centre,  supported 
upon  half  of  a  fire-brick,  in  such  a  situation  that  the  cold  air 
ascending  through  the  grate  may  not  prevent  the  heating  of  its 
bottom.  The  fire  is  then  kindled  and  maintained  by  fresh  sup- 
plies of  fuel,  which  are  added  carefully  so  that  they  may  not, 
whilst  cold,  come  in  contact  with  the  hot  vessel  and  occasion  its 
fracture. 

3.  As  a  wind  furnace. — Wind  furnaces  are   used  for   the 
vitrification  of  mixtures,  reduction  and  fusion  of  metals,  and 
for  other  operations  requiring  a  prolonged  elevation  of  tempera- 
ture. 

The  combustion  is  urged  by  the  draught  of  a  flue,  and  the 
degree  of  heat  within  the  furnace  depends  upon  the  size  and 
height  of  the  chimney  into  which  the  flue  passes.  The  intensity 
of  the  heat  is  increased  by  so  proportioning  the  dimensions  of  the 
furnace  and  the  chimney  that  their  diameters  are  equal,  and 
the  height  of  the  latter  twenty  to  thirty  times  the  diameter  of 
the  former. 

The  furnace  may  be  converted  into  a  wind  furnace  by  putting 
on  the  dome,  closing  all  the  openings,  and  giving  a  free  access 
of  air  to  the  grating  through  a  pipe  attached  to  the  circular 
nozzle  in  the  hearth  space,  and  leading  into  one  of  the  flues  of 
the  laboratory  chimney.  The  smoke-pipe  may  lead  into  the 
same  flue,  and  both  should  be  fitted  with  dampers  for  the  regula- 
tion of  the  draught. 

4.  As  a  blastfurnace. — Blast  furnaces  are  serviceable  for  ex- 
peditiously  producing  a  great  intensity  of  heat,  and  are  used  for 
fusions  and  other  operations  which  require  more  power  than  that 
of  the  wind  furnace. 

The  combustion  is  urged  by  a  current  of  air  forced  through  a 
pair  of  double  bellows,  the  nozzle  of  which  leads  into  the  circular 
opening  near  the  base  of  either  of  the  aforenamed  furnaces.  The 
connection  should  be  tightly  adjusted  with  LUTE,  so  as  to  prevent 
any  escape  of  air.  The  arrangement  otherwise  is  exactly  the 
same  as  for  the  wind  furnace. 

In  blowing  the  blast,  let  the  stream  of  air  entering  the  furnace 
be  small  at  first,  and  be  gradually  increased  as  the  temperature 


ASSAY   OR   CUPEL   FURNACE.     ^  225 

becomes  higher.  The  maximum  heat  can  be  hastened  by  weight- 
ing down  the  bellows,  and  thus  augmenting  the  force  of  the 
blast. 

Sefstrom's  (Berzelius,  vol.  8),  and  Aikin's  (Faraday,  p.  95), 
blast  furnaces  are  said  to  give  heat  sufficient  to  melt  felspar. 

The  blast  may  be  furnished  to  the  preceding  furnaces  from  the 
pneumatic  table,  Fig.  45,  through  a  flexible  leaden  pipe,  connected 
at  either  end  by  means  of  coupling-screws.  As  the  lead  pipe 
might  be  softened  by  a  too  great  proximity  to  the  heated  fur- 
nace, the  opening  in  the  ash  pit  of  the  latter  to  which  the  former 
is  to  be  attached,  should  be  fitted  with  about  two  feet  of  iron  gas 
pipe,  so  as  to  prevent  direct  contact. 

5.  As  an  assay  or  cupel  furnace. — The  same  arrangement 
which   is    directed   for   a   reverberatory 
will  convert  it  into  a  cupel  furnace;  the  Fig.  135. 

only  additional  requisite  being  a  muffle,          /*+ 
Fig.  135,  for  the  reception  of  the  cupels        ( 
in  assaying  operations. 

A  very  convenient  and  more  efficient  furnace  for  CUPELLATION 
is  shown  by  Figs.  136,  137. 

It  is  made  of  refractory  fire  clay,  and  hooped  with  strong  iron 
bands  fastened  together  by  screws,  in  order  that  it  may  better 
withstand  the  high  temperature  to  which  it  is  subjected. 

A,  A',  is  the  ash-pan,  of  diameter  sufficient  for  the  reception  of 
the  body  of  the  furnace  B  B'.  The  door  c,  is  for  the  exit  of  the 
cinders,  and  the  ingress  of  the  air.  The  larger  opening  D',  in  the 
body  of  the  furnace,  is  for  the  introduction  of  the  muffle,  and  a 
corresponding  one  D,  opposite,  for  a  prism-shaped  support  of 
baked  clay  for  maintaining  the  muffle  in  a  horizontal  position. 
The  mouth-piece,  supported  by  a  small  platform,  affords  the 
facility  of  admitting  or  preventing  the  access  of  air  to  the  inte- 
rior of  the  muffle. 

There  are  other  openings  throughout  the  circumference  of  the 
body  immediately  above  the  grate,  for  increasing  the  draught 
when  necessary. 

In  the  part  of  the  dome  E  is  a  door  for  the  introduction  of  the 
fuel.  The  two  openings  e  e  are  for  the  introduction  of  a  poker  to 
arrange  the  fire. 

15 


226 


BARRON S   FURNACE. 


At  the  top  of  the  furnace  is  a  dome  G  G,  to  which  is  adapted  a 
sheet-iron  pipe  for  increasing  the  draught. 


Fig.  136. 


Fig.  137. 


A  sliding  door  H,  and  a  small  circular  gallery  i  i,  as  a  sup- 
port for  heated  coals,  afford  additional  means  of  increasing  the 
draught. 

Barrens  Furnace. — By  far  the  most  convenient  and  generally 
useful  furnace  is  that  known  as  Barron's  Wind-Chest  Table  and 
Blowpipe,  a  portable  apparatus  of  simple  construction.  It  is  not 
only  readily  manageable,  and  economical  as  to  fuel,  but  works 
with  great  efficiency,  being  applicable  for  all  the  purposes  of 
melting,  fluxing,  forging,  annealing,  and  dry  assaying. 

It  consists  of  a  table  with  a  cast-iron  top,  beneath  which  are  a 
wind-chest  and  bellows,  as  shown  by  Plate  3.  Rising  from  the 
wind-chest  and  protruding  through  the  top  of  the  table  are  mov- 
able blow-pipe  jets,  which  convey  the  blast  to  the  furnaces,  of 
which  there  are  four  sizes,  the  smaller  being  capable  of  melting 
4  to  8  ounces  of  gold,  and  the  larger  fifty  times  that  weight. 


• 

-   ••: 


LIEBIG  S  FURNACE. 


227 


The  crucibles  to  be  heated  are  placed  in  the  furnace  in  the  usual 
manner,  and  the  furnace  itself  is  placed  on  the  table  top,  which 
forms  a  convenient  support,  so  that  its  air-tubes  at  the  base  will 
be  immediately  in  front  of  the  nozzle  of  the  blow-pipe.  The 
bellows  is  worked  by  a  treadle,  which  is  adjusted  so  as  to  produce 
a  steady  and  easily  controllable  blast.  Melting  operations  re- 
quire from  5  to  20  minutes,  according  to  the  quantity  of  material 
under  process.  The  arrangement  of  the  furnace  for  assaying, 
annealing,  or  forging,  is  after  the  usual  manner.  By  substituting 
an  oil  or  grease  lamp  for  the  furnace,  the  apparatus  becomes  a 
powerful  soldering  blow-pipe. 

Liebig's  Furnace  for  Organic  Analysis. — This  is  a  small  sheet- 
iron  furnace,  with  movable  partitions  and  screen,  in  which  the 

Fig.  138. 


combustion  of  organic  bodies  is  effected  by  a  charcoal  fire.     Fig. 
138  shows  its  interior.     Fig.  139  gives  a  side  view  of  the  furnace, 

Fig.  139. 


Fig.  140.         Fig.  141. 


containing  a  combustion-tube  under  process  connected  with  orga- 
nic analysis.  It  is  twenty-four  inches  in  length,  three  inches  in 
height,  and  three  inches  in  width  at  the  bottom,  diverging  to  four 
inches  at  the  top.  The  combustion-tube  a  passes  through  a  circu- 
lar opening  in  the  closed  end  of  the  furnace, 
and  rests  upon  sheet-iron  supports,  Fig. 
140.  The  grate  consists  of  a  series  of  slits 
at  the  bottom  of  the  furnace,  which  are 
distant  from  each  other  about  half  an  inch. 
The  sheet-iron  screens,  Fig.  141,  are  used  to  confine  the  fire  to 
certain  parts  of  the  tube. 


W 


228  MANAGEMENT  OF  FURNACES. 

The  furnace  is  used  upon  the  table,  and  should  rest  upon  a 
stone  of  length  nearly  equal  to  its  own. 

Management  of  Furnaces. — All  furnace  operations  should  be 
conducted  under  a  stationary  hood,  so  that  the  carbonic  acid  and 
other  noxious  exhalations  may  have  an  escape  from  the  labora- 
tory, and  the  sparks  and  heated  air  emitted,  be  prevented  from 
endangering  the  comfort  and  safety  of  the  apartment. 

If  the  furnace  is  without  feet,  it  should  rest  upon  a  stone  block, 
and  never  directly  upon  the  floor  or  the  top  of  the  table,  for  its 
heated  bottom  may  occasion  a  conflagration. 

Coal,  coke,  and  charcoal  are  the  fuel  most  used.  Coal  is  the 
least  available,  for  it  contains  sulphur,  and  yields  a  large  amount 
of  ash  and  clinker,  which  choke  the  grating,  and  it  should  never, 
therefore,  be  used  in  the  blast  furnace. 

Coke  and  charcoal,  separately  and  combined,  are  used  for  all 
the  furnace  operations,  the  former  being  preferable  for  assays  at 
a  high  temperature.     Weight  for  weight,  their  amount  of  heat  is 
nearly  equal,  but  the  greater  density  of  the  coke  enables  it  to 
give  more,  bulk  for  bulk,  by  ten  per  cent.     Charcoal  ignites  most 
readily,  but  coke  is  more  durable.     Moreover,  when  of  good 
quality  and  free  from  sulphurous  and  earthy  matter,  it  gives  but 
little  ash  or   clinker.     By  mixing  the  two  together,  the  good 
qualities  of  both  are  obtained  ;  but  charcoal  alone  is  preferable  for 
heating  glass  and  porcelain  vessels.     Before  using  the  coke  or 
charcoal,  care  must  be  taken  that  it  has  been  freed  from  dust  and 
dirt  by  sieving,  and  that  the  pieces  are  about  the  size  of  a  walnut, 
so  that  they  may  pack  away  neither  too  loosely  nor  too  compactly. 
All  of  the  fuel  should  be  kept  in  a  dry  place,  for  the  vapor 
arising  from  wet  coal  and  condensing  upon  the  surface  of  fra- 
gile vessels  which  are  being  heated,  will  be  apt  to  cause  their 
fracture. 

The  crucibles  should  be  placed  in  the  centre  of  the  furnace, 
upon  a  support,  which  may  be  a  piece  of 

Fig.  142.          Fig.  143.         /  -       .        ]  .  *2  V 

fire-brick  or  a  cast-iron  trivet,  as  shown 
by  Fig.  142.     This  support  answers  also 
for  stone-ware  retorts ;  but  a  preferable 
form  for  this  purpose  is  the  crow's-foot, 
Fig.  143.    The  size  of  these  latter  imple- 
ments is  regulated  by  the  proportions  of  the  vessels  which  they 
support. 


THE   FURNITURE   OF   FURNACES. 


229 


.Fig.  144. 


For  supporting  basins  and  flasks  over  the  evaporating  furnace, 
an  iron  trellis  of  strong  wire,  Fig.  144, 
is  necessary.  A  series  of  these  iron 
trellises,  of  different  sized  meshes,  will  be 
found  convenient  for  adapting  the  heat 
to  glass  vessels,  tubes,  &c. 

In  placing  the  vessels  in  the  fire  or  in 
the  sand-bath,  they  must  be  made  to 
stand  firmly,  and  as  near  to  the  centre  as 
possible,  so  that  they  may  be  equally 
heated  all  around.  To  prevent  damage 
to  them  by  a  too  sudden  rise  of  temperature,  the  fire  must  be 
urged  gradually,  and  when  the  operations  are  finished,  they 
should  be  left  to  cool  with  the  furnace,  or,  if  taken  out,  be  trans- 
ferred to  a  cool  sand-bath,  so  that  their  refrigeration  may  not  be 
so  sudden  as  to  cause  fracture. 

When  the  vessel,  to  be  heated  over  the  naked  fire,  is  of  less 
diameter  than  the  mouth  of  the  furnace,  this  latter  may  be  pro- 
portionably  lessened  by  means  of  a  suitably  adapted  flat  iron  ring. 
These  rings,  Figs.  145,  146,  are  also  useful  when  it  is  required  to 


Fig.  145. 


Fig.  146. 


concentrate  the  heat  of  the  furnace  in  the  centre  of  the  vessel, 
and  therefore  it  is  advisable  to  have  a  series  of  them,  the  centre 
openings  of  which  should  decrease  gradually  so  as  to  render  them 
convenient  for  all  sized  vessels.  0,  . 

Before  commencing  operations  the  furnace  must  be  entirely 
freed  from  ashes  and 
clinker,  and  the  coal 
placed  around  the  ves- 
sel in  layers.  When  a 
fresh  supply  of  fuel  is 
requisite,  it  may  be 
added  through  the  door- 


230 


LAMPS. 


14b- 


way  made  for  the  pur- 
pose. The  auxiliary  ap- 
paratus of  a  furnace, 
other  than  that  already 
mentioned,  are  an  ordi- 
nary iron  poker  for  clearing  the  grate  ;  and  several  pairs  of  tongs. 
One  of  these  latter,  for  adding  lumps  of  coal  to  the  fire,  should 
have  the  form  shown  by  Fig.  147.  Those  for  managing  the 
crucible  in  the  furnace  and  for  removing  it  whilst  hot,  may  be 
of  either  of  the  patterns  presented  by  Figs.  148,  149. 

Fig.  149. 


LAMPS. — Lamps  are  convenient  and  economical  substitutes  for 
furnaces  in  table  operations.  Being  less  cumbersome  and  more 
cleanly  than  the  latter,  they  are  readily  manageable  and  always 
ready  for  use ;  and  they  also  afford  the  means  of  more  rapidly 
multiplying  results. 

The  amount  of  heat  to  be  obtained  by  these  instruments  de- 
pends upon  their  size  and  arrangement.  A  properly  constructed 
lamp  may  be  made  subservient  to  all  the  requirements  of  the 
nicer  heating  operations  of  the  laboratory,  from  gentle  digestion 
or  evaporation  to  those  processes  which  require  a  very  high  de- 
gree of  heat. 

The  heating  power  of  the  flame  is  most  active  immediately  be- 
neath its  summit,  and  the  vessel  should  be  gradually  brought 
into  direct  contact  with  that  portion.  The  vessel  should  be 
heated  more  gradually  in  proportion  to  the  thickness.  When 
thick  glass  or  porcelain  or  other  fragile  bad-conducting  material 
is  suddenly  heated,  the  heated  part  expands  while  the  rest  does 
not,  and  this  unequal  tension  of  two  adjacent  parts  causes  the 
cracking  or  fracture  of  the  vessel.  There  is,  therefore,  a  great 
advantage  in  employing  glass  or  porcelain  vessels  of  thin  struc- 
ture, for  the  heat  being  rapidly  conducted  through  them,  the  lia- 
bility of  fracture  is  diminished.  As  strength  is,  however,  often 
required  and  thicker  vessels  must  be  used,  the  above  principles 


LAMPS.  231 

of  expansion  and  conduction  must  be  remembered  when  they  are 
employed. 

In  order  to  apply  a  small  fire  to  a  large  surface,  the  heat  may 
be  diffused  by  setting  the  vessel  in  a  SAND  or  WATER  BATH,  or, 
which  is  convenient  and  more  cleanly,  a  plate  of  sheet  metal  or 
wire  gauze  may  be  placed  between  the  vessel  and  the  fire.  It  is 
safer  not  to  allow  the  vessel  to  touch  the  plate  or  gauze.  Iron 
or  brass  gauze  may  be  used,  although  fine  copper  gauze  is  pre- 
ferable, because  more  durable. 

The  combustible  or  fuel  most  commonly  used  in  chemical  lamps 
is  alcohol,  though  pyroxylic  spirit  and  lamp  oil  are  occasionally 
employed. 

Alcohol  flame  gives  no  smoke  or  unpleasant  odor,  the  product 
of  combustion  being  only  carbonic  acid  and  water ;  while  lamp 
oil,  especially  where  the  supply  of  oil  to  the  wick  is  insufficient, 
produces  a  black  carbonaceous  deposit  upon  the  bottom  of  the 
vessel  which  occasions  a  loss  of  heat  by  radiation. 

The  alcohol  flame  moreover  does  not  have  the  same  injurious 
effect  upon  bodies  in  contact  with  it  as  the  oil  flame  with  its  sooty 
deposit;  nor  does  it  hide  from  view  the  contents  of  test-tubes, 
retorts,  and  other  vessels,  by  blackening  the  glass. 

A  strong  heart  may  be  obtained  from  alcohol,  but  in  tedious 
processes,  which  require  a  long-continued  uniformity  of  tempera- 
ture, the  lest  lamp  oil,  or  better,  olive  oil,  should  be  used,  such,  for 
example,  as  experiments  with  the  mouth  blow-pipe. 

Pyroxylic  spirit  is  much  less  objectionable  than  lamp  oil,  and, 
according  to  Bolley,  nine-fourteenths  cheaper  than  alcohol  in 
heating  capacity.  The  many  other  advantages  of  the  latter, 
however,  give  it  the  preference  over  all  other  combustibles  as  fuel 
for  chemical  lamps.  It  should  be  of  about  the  sp.  gr.  of  0-85. 
Lamps  burning,  should  always  be  extinguished  before  having  the 
supply  of  fuel  renewed,  so  as  to  prevent  liability  of  explosion. 
The  spirit  is  then  gradually  introduced  from  the  tubed  bottle, 
Fig.  55,  p.  83,  until  the  reservoir  is  nearly  full.  This  mode  pre- 
vents its  running  out,  and  diminishes  the  risk  of  overflow  from 
too  large  a  stream.  When  the  lamp  is  not  in  use,  the  wick  should 
always  be  covered  with  the  extinguisher  to  prevent  loss  by  evapo- 
ration. 


232 


GLASS    SPIRIT   LAMP. 


Fig.  151. 


The  tongs  accompanying  these  lamps  are  a  pair  of 
surgeon's  forceps,  of  such  a  form  as  shown  by  Fig. 
150.  As  they  are  liable  to  become  oxidized  by  con- 
stant exposure,  it  is  better  to  have  their  prongs 
plated  with  platinum.  This  precaution  lessens  the 
liability  of  debasing  the  contents  of  crucibles  with 
iron  oxide  which  may  become  detached  when  they  are 
handled  with  rusty  tongs. 

We  proceed  to  speak  of  such  lamps  as  are  suitable  to  labora- 
tory purposes. 

Glass,  Spirit,  Lamp. — This  is  a  small  glass  lamp,  like  the 
one  shown  in  Fig.  151.  The  body  is  the 
reservoir  for  the  alcohol.  To  the  neck 
b  is  adjusted  a  copper  circular  shield  c, 
with  a  tube  in  its  centre  for  the  passage 
of  the  wick,  which  should  be  of  cotton, 
and  similar  to  that  used  for  tallow 
candles.  The  shield  should  rest  upon, 
rather  than  within  the  neck,  otherwise 
its  expansion  by  the  heat  may  cause  the 
breakage  of  the  glass.  A  minute  opening  drilled  in  the  shield  is 
also  requisite  for  the  escape  of  vapor  in  case  the  alcohol  should 
become  heated.  The  glass  cap  a,  ground  interiorly,  so  as  to  fit 
hermetically  to  the  neck  of  the  lamp  when  not  in  use,  prevents 
the  evaporation  of  the  alcohol,  and  the  consequent  impregnation 
of  the  wick  with  water,  which  renders  its  relighting  difficult. 


Fig.  152. 


Fig.  153. 


The   lamp   must,    however,    be   invariably   extinguished    before 
putting  on  the  cap. 

These  lamps  are  useful  for  heating  small  apparatus,  such  as 


BERZELIUS'S   LAMP. 


233 


test-tubes,  Figs.  152,  153,  and  reduction-tubes,  and  for  larger 
vessels  which  require  only  a  gentle  heat,  as  shown  in  Fig.  154. 
They  are  generally  supplied  with  spirit  through  the  mouth  occu- 


Fig.  104. 


pied  by  the  wick-holder.  A  much  safer  and  more  convenient 
mode  would  be  to  pour  it  through  a  channel  in  the  shoulder ;  and 
lamps  are  now  being  made  with  this  provision,  as  shown  in  the 
drawing  which  illustrates  Bunsen's  mode  of  igniting  filters.  The 
heating  power  of  the  lamp  may  be  greatly  augmented  by  the 
use  of  a  small  conical  chimney,  made  of  sheet-mica  or  copper.  It 
may  rest  upon  the  shoulder  of  the  lamp ;  but  to  permit  access  of 
air  must  be  perforated  at  the  base  with  large  holes,  or  else  raised 
on  feet. 

Berzeliuss  Lamp. — Fig.  40  at  page  64  represents  this  lamp 
with  the  improvements  recommended  by  Mitscherlich  and  Liebig. 
It  should  be  made  of  thick  sheet  copper  or  brass,  and  brazed 
instead  of  being  soldered  together.  Its  form  is  that  of  an  Argand 
lamp,  with  a  circular  body  or  reservoir^,  Fig.  155,  which  receives 
its  fuel  through  the  stoppered  opening  r.  The  mechanism  con- 
tained in  the  framework  s,  and  communicating  with  the  cylinder 
£,  allows  the  elevation  or  depression  of  the  wick  at  will.  The  only 
communication  between  this  portion  of  the  lamp  and  the  reser- 
voir is  by  a  small  tube  through  which  the  alcohol  is  supplied  to 
the  wick.  The  chimney  u  may  be  movable  and  adapted  to  a 


234 


CRUCIBLE   JACKET. 


flattened  socket  soldered  to  the  side  of  the  inner  circumference 
of  the  reservoir,  or  else  be  hinged  in  the  same  position,  so  that  it 


Fig.  156. 


may  be  thrown  back  when  the  lamp  is  to  be  lighted  or  trimmed. 
Surmounting  the  chimney  is  a  crucible  jacket  h  with  a  handle  q 
adapted  to  the  socket  or  thumb-screw.  The  crucible,  with  its 
movable  cover  d,  Fig.  156,  is  placed  in  the  centre  of  the  sheet- 
iron  jacket,  upon  supports,  so  as  to  receive 
the  full  force  of  the  flame.  It  is  designed 
to  protect  the  crucible  from  all  air  save 
that  which  passes  up  the  chimney.  The 
whole  arrangement  is  shown  by  Fig.  156, 
c  being  the  chimney  of  the  spirit  lamp, 
and  the  arrows  showing  the  direction  of 
the  flanre,  which  passes  unobstructed  up- 
ward. All  atmospheric  air  save  that 
which  passes  up  the  chimney  being  ex- 
cluded, the  heating  power  of  the  lamp  is 
greatly  increased. 
The  lamp,  as  seen  by  the  figures,  is  mounted  upon  a  fork  t», 


LAMP   SUPPORT. 


235 


which  slides  upon  the  upright  of  the  support  b.  This  upright  is 
a  smooth  wrought-iron  or  brass  rod,  screw  cut  at  its  lower  end, 
and  firmly  fastened  to  the  walnut  foot  b  by  means  of  a  nut.  The 
foot  serves  as  a  ballast,  and  at  the  same  time  as  a  bed  for  a  large 
capsule,  which  is  a  convenient  receptacle  for  any  matter  which 
may  be  accidentally  spilled  from  the  heating  vessel.  The  pan  p 
is  intended  for  the  same  purpose  when  the  support  is  occupied  on 
either  side.  There  are  other  appliances  which  add  to  the  conve- 
nience of  this  lamp.  They  consist  of  thumb-screws  and  sockets 
d  ef  for  holding  the  iron  wire  rings  m  I  i  k.  These  rings,  vary- 
ing in  diameter,  serve  as  supports  for  the  vessels  employed,  and 
to  steady  those  which  are  tall,  like  the  flask  shown  in  the  figure, 
a  clamp  /  is  requisite.  The  thumb-screw,  to  which  the  rings  are 
attached,  slide  upon  the  upright  rod,  and  allow  the  elevation  or 
depression  of  the  heating  vessel  at  will.  The  iron  plate  sand- 
bath  n  is  very  useful  for  digestions  in  beaker  glasses,  which  will 
not  safely  bear  direct  contact  with  the  flame. 

The  fittings  of  this  and  all  other  chemical  lamps  should  com- 
bine lightness  with  strength,  so  as  to  avoid  the  dissipation  of  too 
much  heat  by  excess  of  metal. 

Fig.  157  exhibits  a  lamp  support  not  very  dissimilar  to  the 
preceding,  buf  with  a  cast-iron  triangular  foot  6,  of  weight  suffi- 
cient to  prevent  the  lamp  from  being  upset  by  the  superposition 
of  heavy  vessels.  The  iron  triangle  d  is  a 
very  convenient  substitute  for  the  ring  when 
a  crucible  is  to  be  heated,  as  that  shape  aifords 
a  better  support.  The  rod  a  of  brass  or 
iron  is  from  twenty  to  twenty-four  inches  in 
length.  The  fork  g  for  the  lamp,  and  the 
rings,  are  all  adapted  to  the  thumb-screws 
which  hold  them  steadily  until  they  are  to  be 
replaced  by  others  of  different  form  or  size 
for  different  and  larger  vessels. 

A  very  convenient  modification  of  Berze- 
lius's  lamp  for  boiling  in  large  vessels  is  shown 
by  Fig.  158.  It  is  supported  by  three  feet 
of  solid  brass.  Adjusted  to  its  wooden  handle 
is  a  brass  crook  for  supporting  the  necks  of 
beaked  vessels,  retorts,  and  the  like.  This  crook  can  be  lowered 


Fig.  157. 


236 


LUHME'S  LAMP. 


or  elevated  at  will  by  means  of  the  thumb-screw  by  which  it  is 
fastened.  Two  rings  accompany  it,  one,  of  open  work,  for  the 
support  of  capsules,  broad  and  round  bottomed  vessels ;  and  the 


other  calendered  with  fine  holes,  for  the  distribution  of  the  heat 

to  flat-bottomed  glass  vessels. 

This  is  a  powerful  lamp,  and  is  more  convenient  for  large  vessels 
than  the  lamp  mounted  as  before  de- 
scribed. Luhme",  who  first  recommended 
this  form,  also  advises  that  there  be  no 
direct  communication  between  the  re- 
servoir and  the  circular  space  containing 
the  wick,  because  such  an  arrangement  is 
prornotive  of  accidents.  When  the  lamp 
has  burned  for  a  length  of  time  and 
nearly  all  the  alcohol  is  consumed,  the 
reservoir  becomes  filled  with  vaporized 
spirit,  which  may  explode  when  it  is  relit 
after  being  refilled.  All  this  is  prevented 
by  forming  the  connection  by  means  of 
a  tube.  The  Berzelius  lamps  of  recent 
manufacture  are  made  with  this  improve- 
ment. 

Either  of  these  lamps,  and  all  others 

in  which  spirit  is  consumed,  must  be  provided  with  a  metallic  ex- 


THE   RUSSIAN    LAMP. 


237 


tingulsher  to  protect  the  wick  and  prevent  evaporation  of  the 
alcohol. 

Roses  Lamp. — This  lamp,  Fig.  159,  also  constructed  upon  the 
principle  of  the  Argand  burner,  gives  an  intense  heat.  It  pos- 
sesses the  advantage  recommended  by  Luhme"  of  having  the  re- 
servoir at  a  distance  from  the  burner,  so  that  the  spirit  remains 
unheated  during  the  longest  operations.  The  wick  is  regulated 
by  a  rack  and  pinion  as  in  the  Berzelius  lamps,  and  its  mode  of 
management  is  precisely  the  same. 

The  Russian  Lamp. — This  apparatus,  Fig.  160,  affords  a 
very  powerful  heat  in  a  few  minutes.  It  consists  of  a  strong 
double  brass  cylinder  or  box,  the  interior  arrangement  of  which 
is  shown  by  the  dotted  lines  in  the  cut.  A  piece  of  tube  termi- 
nating in  a  jet  passes  from  the  exterior  to  the  interior  chamber, 
rising  nearly  to  the  top  of  the  former.  The  fuel  is  supplied 
through  the  aperture  £,  closed  with  a  cork,  and  not  with  a  brass 
cap.  The  lamp  is  known  to  be  fully  charged  when  the  spirit 
begins  to  flow  from  the  jet.  The  inner  chamber  is  then  to  be 
filled  with  the  same  spirit  to  within  half  an  inch  of  the  apex  of 
the  jet.  The  ignited  spirit  in  the  inner  chamber  heats  that  in 
the  outer,  and  causes  it  to  boil,  the  pressure  of  the  vapor  forces 
the  boiling  spirit  through  the  jet  in  a  powerful  stream,  which  of 
course  becomes  immediately  inflamed,  and  acts  as  an  energetic 
blast,  producing  heat  enough  to  ignite  a  platinum  crucible,  placed 
above  it,  to  whiteness.  The  triangle  which  supports  the  crucible 
must  be  of  platinum,  and  the  ring  upon  which  the  triangle  rests 
of  very  stout  iron  wire  in  order  to  resist  the  fusing  effect  of  the 


By  enclosing  the  crucible  in  a  Fis- 16°- 

jacket  (Fig.  156),  for  which  the 
rim  of  the  lamp  will  form  a  suffi- 
cient support,  the  action  of  the 
blast  is  greatly  expedited  as  well 
as  augmented. 

There  are  certain  precautions 
necessary  in  the  use  of  this 
lamp,  to  guard  the  operator 
against  accidents.  Before  in- 
troducing the  alcohol,  it  is  proper  to  be  assured  that  the  jet  is 


238 


DEVILLE'S  BLAST  LAMP. 


free  from  impediment  by  blowing  through  it.  The  cork  stopper 
b  must  be  put  in  somewhat  loosely,  so  that  it  may  offer  no  resist- 
ance should  a  stoppage  occur  during  the  operation.  For  still 
greater  safety,  that  part  of  the  lamp  should  be  turned  from  to- 
wards the  experimenter. 

Pyroxylic  spirit  is  the  fuel  recommended ;  and  it  is  said  that  a 
lamp  of  this  construction,  3J  inches  in  height,  3J  inches  in  dia- 
meter, will  burn  with  a  charge  of  four  ounces  of  spirit  for  thirty 
minutes,  which  is  long  enough  for  most  fluxions  with  carbonated 
alkali. 

Hart's  gas  furnace,  hereafter  described,  is  intended  by  the 
inventor  as  a  substitute  for  the  Russia  lamp. 

Devilles  Blast  Lamp. — This  implement,  the  invention  of  St. 
Clair  Deville,  is  designed  for  producing  high  temperatures  with 
the  use  of  alcohol,  wood  spirit,  kerosene,  camphene,  and  similar 
fluids,  as  fuel.  Those  hydro-carburets  which  have  the  lowest 
boiling-point  and  give  the  densest  vapors,  afford  the  greatest  heat. 
The  lamp  is  applicable  for  fusions,  fluxing,  and  ignitions,  and  a 
few  seconds  only  are  necessary  to  raise  the  heat  equal  to  that  of 
melting  iron. 

Fig.  161  is  a  drawing  of  the  apparatus.  "  It  consists  of  a 
reservoir  F,  with  three  tubulures  above, 
T  t  tf.  By  means  of  the  blast  of  a  blow- 
pipe table,  the  air  is  injected  into  F 
through  the  tube  v,  which  is  inserted  in 
T.  The  tubulure  t  carries  the  vertical 
tube  o,  which  has  a  stop-cock  at  R,  and 
divides  above  into  the  two  arms  b  b', 
which  pass  into  a  metallic  box  u,  and 
terminate  in  its  upper  part  with  open  ex- 
tremities cut  off  obliquely.  The  box  u 
contains  the  burning  fluid  e  partly  filling 
it ;  and  it  connects  with  a  reservoir  by  £", 
which  -is  kept  at  a  constant  level.  The 
centre  of  this  box  is  a  cylindrical  tube, 
closed  below,  through  which  passes  the  blow-pipe  e>  a  continua- 
tion of  the  tube  «',  the  left  tubulure  (in  the  figure)  of  the  flask  F. 
The  tube  which  is  at  the  middle  of  the  box  u,  and  envelopes  the 
blow-pipe  c,  has  several  small  holes  u  u  communicating  with  the 
empty  (or  upper)  part  of  the  box  u. 


Fig.  161 


NUNN'S  BLAST  LAMP.  239 

"  Above  the  blowpipe,  and  resting  in  a  furrow  in  the  top  of  the 
box  u,  there  is  a  copper  cup  K,  pierced  at  the  centre  with  a  hole 
for  the  passage  of  the  jet  of  vapor  which  escapes  from  the  holes 
u  u  u,  after  the  bellows  are  put  in  action. 

"  To  prevent  the  burning  fluid  from  becoming  too  much  heated 
there  is  a  trough  s  containing  water.  Before  lighting  the  lamp, 
the  fluid  in  L  is  heated  till  the  water  in  the  trough  boils ;  then 
the  bellows  are  made  to  act,  and  the  jet  of  vapor  is  lighted ;  after 
which  the  heat  disengaged  by  the  lamp  is  sufficient  to  continue 
the  vaporization  of  the  fluid. 

"  Above  the  box  L  there  is  a  chimney  A  having  a  series  of 
holes  around  near  its  bottom  for  drawing  in  air  on  the  flame  of 
the  apparatus." 

Nunris  Blast  Lamp. — In  this  apparatus,  steam  is  made  to 
accomplish  the  purpose  of  a  blow-pipe  table  in  a  very  simple  and 
efficient  manner.  The  fuel  may  be  either  alcohol,  oil,  or  tallow, 
but  each  requires  its  peculiar  burner. 

The  boiler  is  constructed  after  the  manner  of  a  still-body,  and 
with  a  glass  tube  running  up  its  external  side  to  indicate  the 
level  of  the  water  in  the  interior.  Descending  from  about  two 
inches  above  the  boiler,  and  down  through  the  top  to  within  an 
inch  of  the  bottom,  is  a  supply-pipe.  The  pipe  is  close  to  the 
internal  side  of  the  boiler,  and  terminates  at  its  outer  projection 
with  a  stop-cock  attachment,  to  which  is  coupled  a  piece  of  vul- 
canized india-rubber  tubing.  A  safety-valve  and  steam-pipe 
complete  the  arrangement. 

The  boiler  being  filled  with  water  to  half  its  capacity  is  then 
heated  to  boiling  under  a  regulated  pressure,  and  loss  by  evapo- 
ration supplied  by  a  slight  and  continuous  stream  of  fresh  water 
admitted  through  the  supply-pipe.  The  steam  is  then  let  through 
the  pipe,  and  directed  into  the  centre  of  the  flame  of  the  heating 
medium. 

When  alcohol,  naphtha,  or  other  volatile  liquids  are  used,  the 
jet  is  continued  sufficiently  long  to  volatilize  a  portion  of  the  fuel, 
before  the  latter  is  ignited.  Then  after  the  vapor  is  ignited,  the 
steam  is  again  let  in,  and  the  current  maintained  as  long  as  is 
required.  It  is  necessary  that  the  burner  should  be  constantly 
above  the  boiler,  else  the  steadiness  of  the  blast  will  be  embar- 
rassed by  accumulation  of  condensed  steam.  In  an  oil  flame,  the 
jet  of  steam  is  made  to  issue  from  the  centre  of  the  wick.  \ 


240  THE  TABLE  GAS  LAMP. 

Gas  may  also  be  used  with  this  apparatus  even  more  advanta- 
geously than  oil  or  alcohol ;  it  being  only  necessary  to  employ  a 
burner  like  those  adapted  to  compound  blow-pipes,  and  admitting 
steam  through  one  nozzle  and  gas  through  the  other. 

The  Table  G-as  Laryp. — Gas  is  by  far  the  most  economical 
source  of  heat,  being  always  ready  for  use,  easily  manageable, 
and  cleanly.  It  already  replaces  coal  furnaces  in  the  nicer 
ignitions,  fusions,  &c.  As  the  implements  connected  with  its  use 
become  perfected  in  detail,  it  will  supersede  all  other  means  of 
applying  heat  in  a  large  majority  of  laboratory  operations.  It 
may  be  conveniently  led  to  any  part  of  the  laboratory  through 
flexible  caoutchouc  tubes,  for  which  purpose  one  end  of  these 
latter  is  fitted  with  a  brass  nozzle  for  adjustment  to  a  gallows 
screw  at  the  mouth  of  the  gas  tube-feeder  pending  over  the  ope- 
rating table.  The  other  end  terminates  in  either  an  Argand, 
single  jet,  or  other  suitable  burner,  according  to  the  purpose  for 
which  the  flame  is  to  be  applied. 

A  single  jet  answers  very  well  for  the  small  gas  stands  ;  but  for 
use  with  the  blow-pipe  table,  an  Argand  burner  is  necessary. 

The  gas  lamp,  Figs.  41,  42,  which  has  been  fully  described  at 
pp.  64,  66,  supersedes  all  other  heating  apparatus  for  table  ope- 
rations. Crucibles,  capsules,  and  retorts,  are  alike  readily  heated 
by  it,  and  .even  distillations  on  a  large  scale  may  be  successfully 
performed.  To  effect  the  latter  object,  the  upper  half  of  a  black 
lead  or  clay  crucible  may  be  placed  around  the  lamp,  provided 
with  an  opening  on  one  side  for  the  beak  of  a  retort  to  pass  out. 
The  lower  half  of  the  crucible,  with  its  bottom  broken  off,  is  then 
inverted  over  the  whole,  and  the  hole  at  the  top  loosely  covered 
to  allow  the  escape  of  the  products  of  combustion.  By  this  ar- 
rangement, the  heat  of  the  flame  reverberates  through  the  dome, 
and  increases  the  effect  to  such  a  degree  that  several  pounds  of 
mercury  may  be  distilled  at  once  from  the  red  oxide. 

Ga's  being  in  general  use  in  the  large  cities  and  towns,  an 
ample  supply  can  be  obtained  from  the  works  established  for  its 
manufacture  and  distribution.  But,  in  the  country  and  thinly 
inhabited  districts  which  are  not  thus  favored,  the  consumer  must 
depend  upon  private  means  for  this  convenient  and  economical 
heating  as  well  as  illuminating  agent.  Upon  a  limited,  but  suffi- 
cient scale,  for  the  purposes  of  a  small  laboratory,  it  may  be  made 


GAS   FROM   GREASE.  241 

from  grease  with  a  portable  and  inexpensive  apparatus,  devised 
by  Kent,  and  shown  in  the  annexed  drawing. 

Fig.  162. 


The  material  to  be  used  is  the  refuse  fat  of  the  kitchen,  a 
gallon  of  which,  Jn  its  melted  state,  will  yield  100  cubic  feet  of 
oil  gas,  sufficient  to  feed  a  bat-wing  burner  for  upwards  of  seventy 
hours. 

It  consists  of  a  wrought  iron  retort,  thirteen  inches  high  and 
six  inches  in  diameter,  with  a  large  opening  at  the  top  for  the 
passage  of  lumps  of  coke  with  which  it  is  to  be  three-fourths 
filled.  The  coke  is  used  to  increase  the  extent  of  the  heating 
surface  so  as  to  facilitate  and  hasten  the  generation  of  the  gas. 

The  retort  fe  to  be  heated  to  low  redness,  but  no  higher,  other- 
wise the  gas  becomes  decarbonized.  The  oil  is  supplied  to  the 
retort  in  a  thin  but  constant  stream  from  the  funnel,  through  a 
small  hole  in  the  key  of  the  stop-cock.  The  retort  is  connected 
by  an  iron  tube  with  a  copper  reservoir  immersed  in  cold  water, 
for  the  purpose  of  cooling  the  gas.  and  collecting  a  portion  of  un- 
decomposed  oil  which  passes  over.  An  additional  receiver  renders 
this  apparatus  applicable  to  the  purposes  of  illumination  or 
heating.  All  the  pipes  and  appliances  for  either  are  furnished 

16 


242  GAS   FROM   ROSIN. 

•with  the  apparatus  by  the  manufacturer,  to  order.  The  retort 
requires  to  be  occasionally  cleansed,  but  at  no  other  time  has  it 
to  be  necessarily  opened. 

Large  vulcanized  india-rubber  bags  make  excellent  gasometers 
for  small  quantities  of  gas ;  but  for  100  cubic  feet,  it  will  be 
better  to  have  a  sheet-iron  bell  well  payed  over,  internally  and 
exteriorly,  with  plumbago  paint.  The  cistern  for  its  reception  can 
be  sunk  in  the  yard,  and  for  the  above  quantity  its  dimensions 
must  be  6J  feet  diameter  and  4J  feet  depth. 

Gas  is  by  far  the  most  economical  source  of  heat,  being  pow- 
erful, always  ready  for  use,  readily  manageable,  and  cleanly. 
For  all  the  nicer  ignitions,  fluxions,  and  fusions  it  replaces  the 
furnace,  which  is  less  convenient,  and  requires  tenfold  the  time 
for  its  action.  In  five  minutes,  by  the  aid  of  the  table  blow-pipe, 
Fig.  45,  and  appropriate  burners,  we  can  often  satisfactorily  com- 
plete processes  which  with  a  furnace  would  require  an  hour. 
This  saving  of  time  and  fatigue  is  an  important  consideration 
when  the  operations  are  to  be  multiplied  or  rapidly  repeated.  By 
"driving  a  current  of  air  obliquely  and  somewhat  downward 
through  the  Argand  burner,  the  process  of  cupellation  may  be 
accurately  performed  on  three  hundred  grains  of  lead." 

Gas  may  also  be  made,  readily  and  economically,  from  rosin 
or  rosin  oil.  A  very  convenient  arrangement  for  the  purpose  is 
that  exhibited  by  the  following  drawing,  and  known  as  the  "Mary- 
land Co.'s  Portable  Gas  Apparatus."  One,  costing  $350,  com- 
plete, including  expense  of  transportation  and  erection  within  a 
reasonable  distance  from  the  manufactory,  will  produce  and  store, 
in  three  hours,  300  cubic  feet  of  gas,  at  a  total  expense  of  50  to 
75  cents,  only  3  gallons  of  rosin  oil  and  twelve  cents  worth  of 
anthracite  coal  being  consumed  in  the  operation.  Moreover,  very 
little  labor  or  attention  is  required ;  and  as  each  burner  needs 
but  two  cubic  feet  of  gas  per  hour,  the  product  of  a  single  dis- 
tillation will  be  amply  sufficient  to  feed  five  burners  for  four 
hours,  nightly,  during  a  whole  week.  Machines  of  larger  capacity 
cost  in  proportion. 

The  apparatus,  being  of  simple  construction,  is  very  manage- 
able. It  consists  of 

"  1st.  An  oil  can  or  reservoir,  *  A/  for  the  raw  material. 


MANUFACTURE  OF  GAS. 


243 


"2d.  A  stove,  'B,'  in  which  is  set  the  retort  or  Generating 
Apparatus. 

Fig.  163. 


"3d.  A  siphon  box  or  condensing  box — '  C.' 

"4th.  The  water-tank— <  D.' 

"  5th.  The  gas-holder,  i  E,'  which  hangs  into  the  water  of  the 
tank  like  an  inverted  tumbler. 

"The  reservoir  is  a  simple  cylindrical  vessel,  containing  the 
oil  from  which  the  gas  is  generated.  The  retort  is  an  iron  hollow 
cylinder,  with  a  spheroidal  bottom  and  flat  cover,  bolted  and 
screwed  to  a  projecting  rim.  The  stove  containing  the  retort  is 
of  sheet  or  cast  iron,  arranged  upon  the  most  approved  plans  to 
economize  the  heat.  The  siphon  box,  or  condenser  is  a  cast  iron 
vessel,  with  a  movable  lid  bolted  and  screwed  upon  it.  This  is 
divided  into  compartments  and  half  filled  with  water,  with  a 
siphon  attached,  so  as  to  keep  the  water  at  all  times  to  its  proper 
level.  The  water-tank,  in  which  the  gasometer  floats,  is  made 
of  wood  or  iron,  and  placed  upon  the  surface  of  the  graund,  or 
which  is  better,  sunk  to  the  level  of  the  water.  The  gas-holder 
is  of  sheet  iron,  suspended  upon  fixed  pulleys,  and  forms  the  re- 
ceiver for  the  gas,  when  generated  and  ready  for  consumption. 
The  reservoir  communicates  with  the  retort  by  a  feed-pipe,  or  by 
a  feed-pipe  and  cock,  through  a  siphon  screwed  into  the  cover  of 
the  retort. 


244  MANUFACTURE   OF  GAS. 

"  This  siphon  connects  with  a  tube  suspended  perpendicularly 
in  the  middle  of  the  retort,  pierced  with  small  holes  in  its  lower 
end.  Through  this  feed-pipe  and  siphon,  the  liquid  passes  into 
the  tube  thus  suspended,  and  by  the  small  holes  at  the  end  of  the 
tube  becomes  dispersed  upon  the  bottom  and  sides  of  the  retort. 

"  The  working  of  the  machine  and  management  of  it  requires 
no  more  than  ordinary  skill,  and  may  be  safely  intrusted  to  a 
domestic.  A  fire  is  made  in  the  stove  as  in  an  ordinary  furnace, 
and  the  retort  is  heated  to  a  bright  cherry-red  heat.  The  cock 
is  then  opened  to  allow  the  oil  to  pass  in  through  the  pipes  from 
the  reservoir,  upon  the  heated  sides  and  bottom  of  the  retort, 
where  it  is  instantaneously  converted  into  gas. 

"  Ascending  from  this  decomposing  chamber,  the  gas  is  forced 
through  a  superstratum  of  chemical  substances,  suspended  upon 
an  iron  grating,  for  its  purification,  into  a  vacant  upper  chamber, 
and  thence  it  is  conducted  by  an  iron  pipe  into  the  condensing  box. 
This  iron  pipe  passing  through  the  cover  of  the  condensing  box 
descends  below  and  discharges  the  gas  into  the  water  of  the  con- 
densing box.  Thence  it  rises  into  the  vacant  chamber  above 
the  water,  which,  becoming  filled,  forces  the  gas  again  into  the 
water  under  one  of  the  several  compartments  above  referred  to, 
into  a  second  chamber,  and  then  on  through  consecutive  baths 
before  it  finds  its  exit  from  the  last  of  the  series  of  consecutive 
chambers. 

"  This  exit  is  through  a  pipe  which  communicates  from  the 
condenser  with  the  water-tank  into  which  it  enters,  and  passing 
through  the  water  above,  again  descends,  and  discharges  the  gas 
into  the  water  for  its  last  bath, — thence  it  rises  into  the  vacant 
chamber  of  the  gasometer  ready  for  use.  Connected  with  the 
siphon  of  the  condenser  is  a  small  covered  vessel,  which  receives 
the  impurities  washed  from  the  gas  in  its  passage  through  the 
baths.  The  machine  as  above  described,  occupies  a  space  of 
eight  feet  by  twelve,  and  in  height  thirteen  feet,  with  the  tank 
upon  the  ground.  If  the  tank  be  sunk,  then  the  height  will  be 
but  seven  feet. 

"  The  material  used  is  an  oil  from  rosin,  though  not  what  is 
generally  understood  as  rosin  oil.  It  is  an  earlier,  cheaper,  and 
better  product  of  colophony,  decomposable  at  a  lower,  and  there- 
fore more  economical  degree  of  heat." 


MANUFACTURE   OF   GAS. 


245 


The  supply  of  this  material  is  inexhaustible,  and  any  antici- 
pated demand  can  scarcely  enhance  the  price,  which  is  now  12J 
cents  per  gallon.  Each  gallon  of  the  raw  material  may  be  safely 
estimated  to  make  one  hundred  cubic  feet  of  gas. 

When  gas  is  used  it  is  only  necessary  to  bring  the  Argand 
burner,  Fig.  46,  over  the  jet  3,  Fig.  45,  and  to  depress  it  so 

Fig.  164. 


much  that  its  orifice  may  extend  a  short  way  into  the  flame  for 
heating  a  vessel  of  small  surface,  Fig.  164,  and  still  further  for 
vessels  of  greater  superficies.  The  gas  being  turned  on  and  in- 
flamed, the  treadle  is  then  worked  with  the  foot,  slowly  at  first, 
until  the  current  of  air  thus  forced  up  through  the  tube  changes 
the  white  and  quiet  flame  into  one  of  a  pale  reddish  tint  and 
ragged  outline.  If  too  much  air  be  driven  through,  the  flame 
becomes  bluish,  and  the  heat  becomes  less  intense. 

When  a  lamp  is  used,  it  is  necessary  that  it  should  have  a  cir- 
cular Argand  burner,  which  is  to  be  placed  over  the  jet  3,  in  such 
a  position  that  the  orifice  of  the  latter  projects  through  the  centre 
of  the  burner,  just  beyond  the  top  of  the  wick.  The  length  of  the 
flame  being  proportional  to  the  elevation  of  the  wick,  the  latter 
must  be  adjusted  accordingly  by  the  screw  and  rack  before  being 
ignited.  The  flame  being  of  the  proper  height,  the  treadle  4, 


246 


GAS  FURNACES. 


Fig.  165. 


Fig.  45,  is  to  be  worked  at  first  slowly,  for  the  heat  must  be 
gradually  applied,  and  then  more  rapidly  by  increasing  the 
motion  of  the  foot  until  the  blast  produces  a  buzzing  sound,  when 
the  impulse  is  continued  or  moderated  as  the  case  may  require. 

The  crucible  to  be  heated  is  placed  upon  a  wire  triangle,  rest- 
ing upon  a  ring  of  an  upright  support,  as  shown  in  the  figure, 
and  is  placed  over  the  FLAME,  so  that  it  may  be  surrounded  by 
the  upper  or  hotter  portion  (BLOW-PIPE).  If  the  flame  is  smoky, 
and  deposits  carbon  on  the  side  of  the  crucible,  the  blast  must  be 
increased  or  the  flame  lowered. 

The  operation  being  finished,  the  covered  crucible  is  left  to  cool 
before  being  opened. 

Beetle's  G-as  Furnace. — This  apparatus,  Fig.  165,  gives  a  heat 
of  sufficient  power  to  fuse  a  silicate  with 
carbonate  of  soda  in  a  few  minutes.  It  is 
made  very  much  in  the  form  of  an  ordi- 
nary gas  stove,  but  with  a  movable  door, 
having  a  gateway  to  afford  a  view  of  the 
interior,  as  may  be  necessary  to  observe 
the  progress  of  the  operation.  The  body 
of  the  stove,  a  gas  and  air-chamber  «, 
should  be  10  to  12  inches  high  and  3  to  4 
inches  in  diameter.  The  tube  b  conveys 
the  gas  to  the  chamber,  where,  becoming 
mixed  with  air,  it  then  passes  upward 
through  the  meshes  of  the  wire  gauze  dia- 
phragm <?,  where  it  is  ignited  and  allowed 
to  burn.  The  circumference  of  the  rim, 
just  above  the  diaphragm,  is  pierced  with 
holes  for  the  free  admission  of  air  to  the 
burning  flame.  The  support  for  the  cru- 
cibles consists  of  iron  pieces  projecting 
from  a  broad  iron  ring  e,  made  to  fit  the 
furnace.  These  latter  parts  being  movable,  they  may  be  re- 
placed by  others  adapted  to  the  various  sizes  of  crucibles. 

Hoffman's  G-as  Furnace. — This  arrangement,  shown  by  the 
accompanying  drawings,  Figs.  166  and  167,  is  designed  as  a  sub- 
stitute for  Liebig's  Charcoal  Furnace,  in  Organic  Analysis,  and 


GAS  FURNACES. 


247 


for  heating  long  tubes  in  a  horizontal  position.  Its  advantages 
over  coal  fire  are  so  obvious  that  we  will  not  enumerate  them ; 
for  though  faulty  in  some  respects,  it  is  still  a  very  efficient 

Fig.  166. 


implement,  which  gives  a  strong  heat,  and  with  the  means  of 
accurately  regulating  it,  according  to  the  requirements  of  the 
process.  As  in  other  gas  furnaces,  the  gas  is  burned  after  having 
become  mixed  with  sufficient  air  to  produce,  in  its  combustion, 
the  maximum  of  heating  power.  We  are  indebted  to  Liebig's 
Hand-Book  of  Organic  Analysis  for  our  drawings  and  description. 
The  furnace  A,  made  of  wrought-iron  plate,  consists  of  three 
separate  compartments  A,  i,  &,  which  are  supported  by  a  stout 
iron  stand  I  m.  Of  these  three  compartments,  the  two  first  h  and 
i  are  simply  rectangular  boxes  of  iron,  open  at  the  bottom  and 
covered  at  the  top  with  wire  gauze,  and  supplied  by  horizontal 
perforated  gas  pipes  w,  n,  Fig.  167.  The  last  compartment  k 
differs  from  the  preceding  in  being  subdivided  into  four  smaller 
chambers  by  three  diaphragms  0,  p,  q,  the  gas  being  supplied 
by  two  pipes  instead  of  one.  The  lower  pipe  r  r  is  a  counter- 
part of  the  gas-pipe  w,  w,  of  the  other  compartments.  On  the 
other  hand,  the  upper  pipe  s,  «,  supplies  the  gas  to  two  rows  of 
fine  vertical  tubes,  similar  to  those  in  Leslie's  burner,  the  ex- 
tremities of  which  project  through  the  wire  gauze  cover  of  the 
compartment,  as  seen  in  Fig.  167.  Each  pipe  is  provided  with 


248 


GAS  FURNACES. 


Fig.  167. 


air-tight  pistons,  by  which 
the  heat  is  entirely  under 
the  control  of  the  operator. 
A  frame  x,  above  the  wire 
gauze,  as  shown  by  Fig.  167, 
supports  the  tube  contain- 
ing the  matters  to  be  heat- 
ed ;  and  in  the  same  draw- 
ing, there  is  a  view  of  one 
of  the  side  pieces  #,  fast- 
ened to  the  frame  by  tongues 
z,  in  such  a  manner  as  to 
form  a  dome  for  reflecting  the  heat  downwards  upon  the  combus- 
tion-tube. 

To  afford  an  intelligent  expression  of  the  manner  in  which  this 
furnace  operates,  we  present  a  view  of  it,  Fig.  168,  as  arranged 
for  performing  combustion  in  an  organic  analysis  in  a  mixed  at- 
mosphere of  air  and  oxygen. 

A  is  the  furnace,  fed  with  the  gas,  through  tubes  a,  5,  c,  d, 
which  are  fitted  with  stop-cocks  e,  f.  The  combustion-tube,  con- 
taining the  matters  to  be  heated,  and  supported  in  the  usual 
manner,  as  shown  at  $r,  communicates,  in  the  usual  manner,  with 
a  chloride  of  calcium  tube  B,  a  bulb  apparatus  c,  and  a  U  tube  D, 
for  solid  potassa.  In  the  rear  is  a  series  of  tubes  containing 
hygroscopic  substances,  for  abstracting  carbonic  acid  and  moisture 
from  the  air  and  oxygen,  as  they  pass  from  the  gasometers  H,  I, 
into  the  combustion-tube.  Of  this  series,  E  contains  solid  potassa, 
and  F  pumice-stone  impregnated  with  sulphuric  acid.  There  is  a 
third  piece  or  bottle  G,  containing  oil  of  vitriol,  and  which  serves 
the  double  purpose  of  a  bubble-gauge  for  measuring  the  rapidity 
of  the  current. 

The  joints  being  all  tight,  gas  is  then  let  on  through  the  flexi- 
ble tube  d  to  the  lower  gas-pipe  r  r,  and  the  piston  u  pushed  so 
far  from  the  inlet  as  to  supply  the  gas  to  the  chamber  0,  I  (Fig. 
166)  only,  whilst  it  is  excluded  from  the  other  chambers.  The 
air-flame  thus  obtained  keeps  the  rear  end  of  the  combustion-tube 
at  a  dull  red  heat.  The  cock  c  is  next  opened,  so  as  to  admit  a 
small  quantity  of  gas  into  the  upper  gas-pipe  s  8,  and  the  piston 
at  the  same  time  drawn  so  far  from  the  inlet  as  to  confine  the  gas 


GAS   FURNACES. 


249 


to  a  very  few  of  the  little  tubes,  at  the  extremity  of  which  more 

Fig.  168. 


points  of  flame  are  thus  produced.     Succeeding  portions  of  the 


250  GAS  FURNACES. 

tube  are  heated  at  the  proper  periods  by  gradually  pushing  in 
the  piston  u  of  the  lower  tube,  and  supplying  gas  to  all  the 
chambers  of  the  compartment  Jc,  until  the  whole  length  of  the 
tube  is  exposed  to  a  uniform  air-flame. 

This  arrangement  affords  great  facility  in  heating  tubes,  with 
the  least  possible  expenditure  of  labor  and  time,  as  well  as  of 
money ;  for  the  cost  of  the  gas  consumed  is  very  trifling,  and  the 
heating-tubes  are  rarely  injured  or  broken,  provided  sufficient  care 
has  been  observed  to  heat  it  gradually  in  the  first  part  of  the  ope- 
ration. As  a  great  security  against  cracking  the  tubes,  the  gas 
should  be  first  lighted  below  the  wire  gauze  and  extinguished 
after  the  furnace  has  acquired  warmth.  It  is  then  to  be  imme- 
diately lighted  again  above  the  gauze. 

The  wire  gauze  becomes  choked  by  use,  and  requires  to  be 
frequently  renewed ;  on  which  account  the  furnace  is  constructed 
so  that  this  repair  may  be  easily  made  by  the  operator,  without 
the  assistance  of  a  gas-fitter. 

The  apparatus  being  arranged  into  three  divisions  is  adapted 
for  operations  with  short  tubes  as  well  as  with  those  of  medium 
and  greater  length. 

Hart's  Gf-as  Furnace. — This  is  a  modification  of  Nunn's  Blast 
Lamp,  in  which  the  combined  action  of  a  steam  jet  and  a  gas 
flame  is  made  an  effective  means  of  producing  heat  sufficient  for 
all  the  ordinary  operations  performed  in  platinum  crucibles.  It 
is  simple  and  inexpensive,  and  works  very  much  like  a  Russia 
lamp,  so  that  it  requires  very  little  watching. 

The  apparatus  is  formed  of  a  round  copper  basin  a,  five  inches 
in  diameter,  and  fitted  by  brazing  with  a  close  circular  top  of  the 

same  metal.  Rising  through 
the  centre  of  this  top  is  a 
small  copper  tube  6,  serving 
as  the  jet.  It  is  inserted 
in  an  elbow-joint  c,  to  which 
is  attached,  laterally,  a  short 
piece  of  gas  tube  d.  There 

is  another  tube  opening  at  e,  for  the  admission  of  water.  To  set 
the  furnace  in  operation,  it  is  only  necessary  to  fill  the  basin  a 
half  full  of  water,  and  after  having  corked  the  tube  b  tightly,  to 
place  it  on  the  ring  of  a  retort-stand  over  a  gas  flame.  In  the 


COMPOUND  BLOW-PIPE.  251 

mean  time,  a  flexible  tube  attachment  is  made  at  d,  for  the  pur- 
pose of  supplying  gas  from  one  of  the  laboratory  burners.  As 
soon  as  the  water  boils  and  steam  begins  to  issue  through  the  jet, 
the  gas  is  turned  on  and  lit  at  c.  The  flame  produced  is  a  hot  blue 
brush ;  and  care  must  be  observed  to  rightly  proportion  the  size 
of  the  flame  and  pressure  of  the  steam  current,  so  as  to  obtain  its 
maximum  of  heat,  and  prevent  the  former  from  being  extinguished 
by  the  power  of  the  blast.  The  jet  must  be  always  kept  free,  and 
to  this  end  should  be  probed  with  a  pin  immediately  before  use. 

Compound  Blow-Pipe. — This  apparatus,  known  as  Hare's 
oxyhydrogen  blow-pipe,  is  used  for  the  fusion  of  such  refractory 
but  fusible  substances  as  resist  the  highest  power  of  the  furnace. 
Its  action  is  based  upon  the  intense  heat  produced  by  the  ignition 
of  combined  oxygen  and  hydrogen  gases,  and  is  fully  explained 
under  the  head  of  BLOW-PIPE  in  Booth's  Encyclopaedia  of  Che- 
mistry. Explanatory  drawings  of  one  of  these  implements, 
adapted  for  large  operations  in  the  arts,  are  to  be  seen  in  Apple- 
ton's  Dictionary  of  Mechanics  and  Engineering,  vol.  i,  p.  107. 
Our  remarks  will  refer  to  economical  forms  of  the  apparatus, 
suitable  for  laboratory  purposes. 

Fig.  170  exhibits  Kent's  pattern.     It  consists  of  two  vulcanized 

Fig.  170. 


india-rubber  bags  or  reservoirs,  of  twenty  gallons  or  greater 
capacity.     These  bags  are  very  flexible,  strong,  and  portable ; 


252  COMPOUND  BLOW-PIPE. 

one  of  the  above  size,  when  empty,  occupying  but  a  very  limited 
space.  They  are  filled,  the  one  with  oxygen,  and  the  other  with 
hydrogen  gas,  each  being  fitted  with  a  connecting  screw  and 
etop-cock,  by  which  they  can  be  adjusted  directly  to  the  genera- 
ting apparatus,  as  shown  by:Fig.  171,  or  with  a  gasometer,  when 

Fig.  171. 


they  are  to  be  charged.  The  communication  between  the  bags  and 
the  jet-pipe  above  the  table  is  by  means  of  the  flexible  india-rub- 
ber or  lead  tubes,  coupled  by  gallows  screws,  Fig.  171.  The 
jets  are  so  divided  within  the  pipe  that  the  gases  enter  at  oppo- 
site ends,  and  consequently  are  not  mixed  until  they  meet  at  the 
arm  of  the  jet,  which  is  so  arranged  that  it  can  be  raised  or 
lowered  on  an  ordinary  retort  stand.  By  this  arrangement, 
which  is  a  convenient  modification  of  the  old  double-jet,  a  jet  of 
oxygen  passes  through  the  centre  of  a  circular  flame  of  hydrogen, 
the  mixture  and  consequent  explosion  of  gases  being  avoided. 

The  gradual  efflux  of  the  gas  from  the  reservoirs  is  effected  by 
superposed  weights, — a  much  more  convenient  mode  than  that  of 
hydrostatic  pressure,  which  is  requisite  when  metallic  reservoirs 
are  used. 

The  two  gases  are  very  readily  prepared.  The  whole  appara- 
tus for  oxygen  is  shown  in  Fig.  171.  The  retort,  a  thin  copper 
flask,  is  connected  with  a  brass  cap  and  neck  by  a  gallows  screw. 

Four  ounces  of  good  chlorate  of  potassa,  and  one  ounce  of  per- 
oxide of  manganese  are  mixed  together  and  placed  in  the  retort, 
the  cap  screwed  down,  and  the  joints  luted  with  pipe-clay.  The 
heat  of  a  Berzelius  lamp,  applied  as  shown  in  the  figure,  drives 
over  ten  gallons  of  pure  oxygen  in  fifteen  minutes. 


GENERATION  OF  HYDROGEN  GAS.  253 

The  lamp  may  be  removed  as  soon  as  the  gas  begins  to  be 
generated  and  pass  over  freely,  as  sufficient  heat  will  be  retained 
for  the  completion  of  the  operation.  The  caput  mortuum  of 
chloride  of  potassium  and  oxide  of  manganese  remaining  in  the 
retort  can  readily  be  removed  by  water. 

Hydrogen  can  still  more  readily  be  obtained  from  a  self-regu- 
lating reservoir.  Fig.  172  exhibits  the  apparatus  as  made  by 

Fig.  172. 


Kent.  The  copper  cylinder  which  he  uses  is  replaced  in  other 
similar  instruments  by  glass.  It  consists  of  a  japanned  copper 
cylinder,  9  inches  high,  and  6  inches  diameter,  with  a  cover  and 
bell  attached. 

Within  the  bell  hangs  a  basket  of  copper  wire,  which  is  to  be 
filled  with  about  f  Ib.  of  zinc,  in  lumps.  The  outer  cylinder  is 
to  contain  6  Ibs.  of  cold  diluted  sulphuric  acid,  made  with  1 
part  acid  to  4  of  water. 

In  the  upper  part  of  the  bell  is  a  division,  forming  a  recep- 
tacle for  a  strong  solution  of  potash,  2  f .  3  of  which  are  put  into 
it  through  the  opening  in  the  top,  which  is  then  to  be  tightly 
stopped. 

The  apparatus  being  adjusted,  and  the  stop-cocks  opened,  the 
dilute  acid  rises  in  contact  with  the  zinc,  and  generates  hydro- 
gen gas,  which,  being  forced  through  the  potassa  solutions,  be- 
comes washed  previous  to  its  exit  from  the  stop-cock  into  the 
bag.  An  hour  suffices  to  generate  twenty  gallons  of  gas ;  and, 
when  it  is  desired  to  arrest  the  operation,  close  the  stop-cock  so 
as  to  produce  an  accumulation  of  gas  in  the  bell,  and  thus  dis- 


254 


DRUMMOND   LIGHT. 


place  the  acid.  The  action  may  be  renewed  at  any  time  by  open- 
ing the  cock. 

Accompanying  this  apparatus,  as  shown  by  separate  figures  in 
the  cut,  are  two  convenient  addenda  for  other  purposes ;  one  a 
jet,  with  platina  sponge  and  fixtures,  for  producing  an  instanta- 
neous light,  and  the  other  for  bending  glass  tubes,  &c.  They 
are  both  readily  attached  to  the  stop-cock  by  their  screws.  In 
the  first  case,  the  gas  is  projected  against  the  platina  sponge,  and 
becoming  immediately  ignited  affords  a  ready  means  of  lighting 
a  taper.  The  sponge,  when  not  in  use,  should  be  kept  covered 
and  dry. 

The  oxyhydrogen  blow-pipe  is  put  into  operation  by  first  charg- 
ing the  bags  with  gases,  placing  on  their  weights,  letting  on  the 
hydrogen,  igniting  it,  and  passing  a  jet  of  oxygen  through  the 
flame  directed  upon  the  substance  under  process.  This  substance 
should  rest  upon  charcoal  or  fire-brick,  and  in  a  cavity  drilled  for 
the  purpose,  so  as  to  prevent  its  being  blown  away  by  the  force 
of  the  blast.  For  the  same  reason,  when  the  substance  is  in 
powder,  it  is  necessary  to  moisten  it  with  water,  and  compress  it 
in  the  cavity.  The  charcoal  rest  is  very  conveniently  supported 


Fig.  173. 


Fig.  174. 


upon  one  of  the  sliding  rings  (Fig.  173),  which  allows  the  facility 
of  bringing  it  near  to  the  orifice  of  the  pipe  where  the  combustion 
takes  place. 

The  heat  thus  produced  is  very  intense,  and  melts  platinum 


RITCHIE'S  COMPOUND  BLOW-PIPE. 


255 


readily.  Coal  or  illuminating  gas  may  be  substituted  for  the 
hydrogen. 

When  this  apparatus  is  used  for  the  purposes  of  illumination, 
as  in  the  production  of  the  Drummond  light,  which  is  produced 
by  the  action  of  its  flame  upon  a  cylinder  of  lime,  the  nozzle  of 
the  blow-pipe  must  be  pointed  upwards,  so  that  the  flame  may 
have  full  play  upon  the  incandescent  earth. 

Another  form  of  compound  blow-pipe,  as  made  by  Ritchie,  is 
shown  in  the  annexed  figure. 

Fig.  175. 


The  gas-holders  are  a  pair  of  metallic  vessels  placed  upon  a 
framework  which  moves  on  castors.  These  vessels  consist  seve- 
rally of  an  outer  bell  and  inner  cylinder,  the  latter  being  sus- 
pended in  the  former  by  counterpoise  weights  concealed  in  the 
posts  of  the  stand.  Self-adjustment  is  thus  secured  in  propor- 
tion as  gas  enters  or  passes  out  of  the  gasometer,  and  very  little 
water  need  be  used. 

The  drawings  show  the'two  gasometers  attached  as  a  compound 
blow-pipe,  with  all  its  necessary  appurtenances,  tubes,  stop-cocks, 


256 


TATE'S  COMPOUND  BLOW-PIPE. 


Fig.  176. 


flexible  hose  with  jets  and  adjustable  holder.  As  each,  however, 
has  its  distinct  inlet-pipe,  screw-plug,  &c.,  they  may  be  used 
separately  for  other  purposes. 

Tate  has  proposed  a  form  much  simpler  and  more  economical 
than  either  of  the  preceding.  It  moreover  answers  the  double 
purpose  of  an  oxyhydrogen  blow-pipe  and  gas-holder.  It  consists 
of  a  receiver  r,  Fig.  176,  with  a  shelf  s,  adjustable  to  b  by  a  screw 
connection.  Like  other  gasometers  it  is  provided  with  stop-cocks 
e,  e.  The  inlet-pipe  is  at  p,  and  the  jet  at  g.  At  the  thick  part 
h  of  this  jet  there  is  a  wire  gauze  diaphragm.  When  the  appa- 
ratus is  to  be  used  as  a  blow-pipe,  the  receiver  must  be  filled  with 
water  to  d,  and  the  mouth  b  closed  with  a  tight  cork  ;  after  which 
a  gas-bag  containing  a  mixture  of  oxygen  and  hydrogen  is  con- 
nected by  a  flexible  tube  attachment 
to  a  bent  metal  pipe  Jc,  n,  passing 
into  the  interior  of  the  receiver. 
When  pressure  is  then  applied  to  the 
bag  a  current  of  mixed  gases  passes 
out  and  upwards  through  the  water 
into  the  tubular  portion  d,  b,  of  two 
inches  height,  and  f  inches  internal 
diameter.  Thence  it  passes  through 
the  jet  upon  the  opening  of  the  cock 
thereof,  and  may  be  ignited  as  it 
issues.  There  is  perfect  safety  in  the 
arrangement,  for,  if  by  chance,  the 
flame  in  the  jet  should  rush  back,  any 
explosion  that  it  might  produce  would 
be  trifling  and  restricted  to  the  small 
volume  of  gas  in  d,  6,  as  the  water  in 
r  prevents  communication  with  the  gases  in  the  bag  reservoir. 

To  convert  the  apparatus  into  a  gas-holder,  it  is  only  necessary 
to  remove  the  jet  or  shut  off  communication  with  it  by  closing 
the  cock  e,  screwing  on  the  shelf  at  &,  and  replacing  the  flexible 
tube  and  gas-bag  by  the  funnel/,  v.  The  inlet p  is  then  opened 
for  the  admission  of  gas  from  a  flask  or  generator.  Pressure  is 
applied  by  a  column  of  water  descending  through  /,  v ;  and  the 
outlet  for  the  gas  is  at  *,  e. 


LAMPS.  257 

Sonnenschein  8  Blast-Lamp. — Ritchie  has  introduced  another 
form  of  compound  blow-pipe,  which  occupies  no  more  room  than 
a  Berzelius  lamp,  and  is  both  convenient  and  efficient  for  blowing 
glass  and  heating  crucibles  to  a  high  temperature.  It  differs  in 
construction  from  the  preceding,  but  assimilates  to  them  in  prin- 
ciple, the  heating  medium  being  the  flame  produced  by  combustion 
of  a  mixture  of  atmospheric  air  and  illuminating  gas.  The  whole 
arrangement  is  shown  by  Fig.  177,  and  consists  of  an  upright 

Fig.  177. 


stand  A,  steadied  by  a  heavy  foot,  and  upon  which  slides  the  brass 
lamp  B  by  its  bulb  £,  fitted  with  a  binding-screw  x,  for  adjusting 
it  upon  the  rod  at  any  required  height.  Projecting  from  this 
bulb  are  two  opposite  branches,  the  one  at  the  left  having  a  stop- 
cock 5,  with  a  screw-end  c  for  the  adjustment  of  a  flexible  tube  #, 
connected  by  a  gallows  screw  with  the  table  or  building  gas-pipe. 
The  right  branch  is^rather  more  compli- 
cated in  structure,  and  consists  of  two 
parts,  one  of  which,  e  /,  is  fixed  hori- 
zontally in  the  ball  e,  while  the  other, 
h  ra,  is  appended  to  it  by  two  movable 
joints,  so  as  to  impart  both  a  horizontal  and  vertical  motion,  and 
thus  afford  the  convenience  of  giving  the  jet  any  desired  bearing. 
The  tube  h  ra,  is  concentric,  as  shown  nearly  in  full  size  by  Fig. 
178,  so  that  the  gas  passes  forward  uninterruptedly  through  e^  g, 
h,  and  between  the  tubes  to  the  point  of  issue  m,  where  it  is  met 

17 


258 


LAMPS. 


by  a  current  of  air  emerging  from  the  smaller  centre  tube,  -which 
is  distinct  from  the  outer,  and  communicates  with  the  ball  ?,  and 
thence  by  a  flexible  tube  i  with  a  bellows  or  blast-table.  The 
inner  tube  is  a  quarter  inch  shorter  than  the  outer  one,  and  ends 
in  a  pointed  jet,  so  that  the  admixture  of  gas  and  air  takes  place 
just  behind  the  point  at  which  they  are  ignited.  This  precaution 
prevents  accident  from  explosions.  To  give  the  apparatus  its 
maximum  force  the  air  may  be  heated  as  it  passes  forward  by 
merely  placing  a  spirit  lamp  under  the  ball  I.  A  veritable  hot 
blast  is  thus  produced. 

The  above  lamp  is  also  made  after  a  modified  pattern,  so  as  to 
bring  into  service,  simultaneously,  an  assemblage  of  jets.  The 
drawing  below,  Fig.  179,  explains  the  arrangement,  which  rests 

Fig.  179. 


upon  the  top  of  a  blow-pipe  or  blast-table,  from  which  rises  an 
air-pipe  i.  The  gas  connection  is  made  by  means  of  the  flexible 
pipe  «,  and  each  jet  being  concentric,  the  gases  only  mix  at  the 
points  of  issue,  as  in  the  apparatus  before  described.  This  com- 
bination of  jets  produces  a  heat  of  great  intensity. 


SUPPORTS — TRIANGLES. 


259 


When  crucibles  are  under  process  with  this  apparatus,  they 
should  be  firmly  secured  upon  the  supports,  and  placed  either 
above  or  below  the  jet.  For  ordinary  purposes  the  breath  will 
answer  the  place  of  a  bellows. 

Supports. — In  lamp,  table  furnace,  and  blow-pipe  operations, 
vessels  are  maintained  in  a  required  position  by  supports,  differ- 
ing in  material  and  construction  with  the  uses  for  which  they  are 
destined. 

A  very  simple  and  economical  support  is  shown  in  Figs.  173 
and  174,  the  only  difference  between  the  two  being  in  the  shape 
of  the  foot,  one  being  rectangular  and  the  other  round.  It  con- 
sists of  an  upright  iron  rod,  from  20  to  24  inches  long,  arid  about 
J  of  an  inch  or  more  in  diameter,  screwed  into  a  cast-iron  foot, 
and  fastened  beneath  by  a  nut.  The  three  projecting-rings,  of 
iron  wire,  2,  3,  and  4  inches  in  diameter,  are  held  by  thumb- 
screws, which  permit  their  elevation  or  depression  at  will. 

For  the  larger  stands  the  thumb-screw  is  of  iron,  and  of  the 
form  exhibited  in  Fig.  164  and  Figs.  180, 182,  b.  It  is  made  with 

Fig.  180. 


two  holes,  at  right  angles  to  each  other,  and  two  screws,  one  for 
the  reception  of  the  iron  upright,  and  the  other  for  the  handle  of 
the  ring,  which  can  readily  be  detached  and  replaced  by  another 
of  different  size.  This  form  of  screw  and  socket  prevents  the 
necessity  and  expense  of  having  the  rings  attached  to  the  screws. 
One  of  these  screws  will  answer  for  a  series  of  rings,  and  the 
latter  being  of  iron  wire,  the  operator  can 
readily  form  them  himself  of  any  required 
shape.  With  this  arrangement,  and  a 
series  of  different-sized  rings,  the  support 
is  convenient  for  all  its  purposes  without 
the  expense  of  a  socket  for  each  ring. 
When  the  rings  are  too  large  for  the  ves- 
sels to  be  heated,  their  diameters  may  be 


Fis.  181. 


260 


THE   UNIVERSAL   SUPPORT. 


Fig.  182. 


diminished  by  means  of  stiff  wire  triangles,  Fig.  181,  called 
trivets.  They  are-  particularly  useful  for  the  support  of  small 
crucibles,  as  is  shown  in  Fig.  41,  p.  64.  There  should  be  a 
number  of  them  of  different  sizes. 

Fig.  182  exhibits  what  is  called  the  "  universal  support."    The 

foot  is  of  cast  iron,  and  the  toes 
twelve  inches  apart.  The  up- 
right rod  is  of  iron,  36  inches 
long,  and  -|  in  diameter.  It  is 
substantially  made,  for  the  sup- 
port of  heavy  capsules,  retorts, 
&c.  The  thumb-screw  and 
sockets  b  are  of  solid  brass  or 
iron.  A  brass  vice,  6  inches 
long,  and  1J  inches  wide,  lined 
in  its  mouth  with  buckskin,  is 
shown  at  g.  It  is  fitted  by  the 
arm  /  to  the  hole  c,  and  serves 
for  the  support  of  heavy  retorts 
and  other  beaked  vessels,  as 
shown  in  the  figure.  Three  solid 

brass  rings,  of  from  4  to  7  inches  diameter,  accompany  this  stand, 
and  are  held  in  the  socket  d  by  the  thumb-screw  a.  As  the  arm 
of  each  of  these  rings  is  adapted  to  the  socket,  one  may  replace 
the  other  when  it  is  desired  to  change  the  size. 

Wooden  supports  adapted  for  tube  arrangements,  made  of  box- 
wood or  hickory,  and  lined  with  cork  or  buckskin  at  the  parts 
intended  for  grasping,  are  also  convenient  and  necessary  pieces 


Fig.  183. 


Fig.  184. 


Fig.  185. 


of  apparatus.  They  consist  of  foot,  rod,  and  nut,  similar  to  the 
iron  supports.  Their  other  parts  are  a  wooden  vice  (Gay- 
Lussac's),  Fig.  183,  for  supporting  the  necks  of  retorts  and  other 


WOODEN   SUPPORTS. 


261 


beaked  vessels ;  Gahn's  cylinder-holder,  Fig.  184,  for  experiments 
with  gases ;  and  a  wooden  ring,  Fig.  183,  as  a  rest  for  inverted 


Fig.  186. 


Fig.  187. 


flasks.  Figs.  186,  187  exhibit  an  upright  retort  clamp  with  a 
movable  joint  and  wooden  screw,  by  which  it  can  be  raised  or 
lowered  at  pleasure.  The  stand  or  lower  portion  is  similar  in 


*Fig.  188. 


Fig.  189. 


construction  to  D  E,  Fig.  191.     Another  form  of  vertical  holder 
for  supporting  horizontal  tubes,  &c.,  is  shown  by  Fig.  186. 


9 

262 


WOODEN    SUPPORTS. 


Fig.  188  represents  another  support,  with  two  sliding  arms,  the 
upper  one  of  which  is  a  funnel-stand,  and  the  lower  a  tube  or 
retort-holder.  The  funnel  supports  of  the  upper  arm  are  adjusted 
thereto  by  means  of  wooden  thumb-screws,  and  may  be  removed 
at  pleasure.  These  are  less  convenient  than  the  single  filter- 
stands,  Figs.  189  and  190,  though  they  have  the  advantage  of 


Fig.  190. 


Fig.  191. 


allowing  several  simultaneous  filtrations  upon  one  arm,  and  thus 
a  single  stand  may  do  the  service  of  three  or  four,  according  to 
the  length  of  the  arm.  The  uprights  of  these  supports  should  be 
screw-cut  at  the  lower  end,  and  fastened  to  their  pedestals  by 
means  of  nuts,  which  retain  them  in  place  more  firmly  than  any 
other  mode. 

A  form  of  stand,  known  as  Berzelius's  table  support,  is  shown 
by  Fig.  191.  It  is  of  hard  wood,  and  consists  of  a  loaded  foot  D, 
supporting  a  flat  disk  A,  which,  by  means  of  its  leg  and  the 
thumb-screw  E,  can  be  raised  or  lowered  to  any  desired  height. 
This  is  a  very  convenient  rest  for  a  small  lamp  or  furnace,  or  for 
recipients  in  distillations,  when  it  is  required  to  raise  either  above 
the  level  of  the  operating-table.  When  in  this  or  other  cases 
the  surface  of  the  supported  vessel  is  round,  it  is  safer  to  steady 
it  upon  a  braided  straw  ring,  Fig.  192,  interposed  between  its 
bottom  and  the  disk. 


TUBE  AND  BULB  RESTS. 


263 


Fig.  192. 


For  supporting  tubes  and  other  vessels  horizon- 
tally, the  disk  may  be  replaced  by  the  brass  crook, 
as  shown  in  Fig.  193 ;  and  for  globular  vessels  and 
flasks  by  the  wooden  tripod,  Fig.  194,  or,  still 
better,  a  wooden  bowl.  Each  of  these  pieces  is 
adapted  to  the  stand  D,  and  one  may  replace  the  other  when 
necessary,  the  screw  allowing  them  to  be  raised  and  steadily 
maintained  at  the  required  height.  The  height  of  this  instru- 
ment, when  drawn  out  to  its  full  length,  is  twenty  inches. 


Fig.  194. 


Fig.  195. 


As  a  support  for  large  evaporating  vessels  over  furnaces,  an 
iron  tripod,  Fig.  195,  is  very  convenient. 

The  test-tube  stand  or  rack,  which  is  the  only  support  that 
remains  to  be  mentioned,  has  been  alluded  to  before,  p.  63,  Fig. 
39.  A  smaller  one  for  table  use  is  shown  in  Fig.  196.  It  con- 
sists of  two  narrow  uprights,  say  ten  inches  high,  of  thin  poplar 
wood,  which  are  braced  together  by  three  shelves.  These  shelves 
are  perforated  throughout  their  length  with  auger-holes  for  the 
reception  of  the  test-tubes.  The  smaller  and  shorter  tubes  occupy 
the  upper  range ;  the  interval  between 
which  and  the  middle  shelf  should  be 
less  by  an  inch  than  that  between  it 
and  the  lower. 

The  manifold  uses  of  the  aforemen- 
tioned instruments  will  be  more  fully 
explained  when  we  refer  to  manipula- 
tions for  which  they  are  applicable. 
At  present,  a  familiar  idea  may  be 
obtained  by  reference  to  Figs.  152,  154,  155,  and  to  the  cut 


Fig.  196. 


264 


BATHS. 


below,  in  which  several  of  them,  as  applied  in  operations,  are 
included. 

Fig.  197. 


CHAPTER  XII. 

BATHS. 

CUE  remarks  in  this  chapter  will  refer  to  the  means  by  which 
the  fire  heat  is  moderated  and  diffused,  before  being  applied  to  the 
containing  vessels  of  substances  under  process.  These  means 
consist  of  baths,  which  are  called  vapor,  water,  saline,  metallic, 
oil,  or  sand,  according  to  the  nature  of  the  interposed  bodies  em- 
ployed. 

The  object  of  an  intermedium  is  to  prevent  a  too  rapid  appli- 
cation of  heat,  and  to  give  greater  uniformity  of  temperature. 
Inequality  and  too  sudden  application  of  heat  being  thus  provided 
against,  the  fracture  of  vessels  and  ejection  of  their  contents,  and 
many  inconveniencies  attending  other  modes  of  applying  heat,  are 
avoided. 

Baths  are  very  convenient  for  heating  substances  which  re- 
quire a  constant  and  somewhat  permanent  elevation  of  tempera- 


CONSTRUCTION   OF   BATHS.  265 

ture,  and  which  might  undergo  decomposition  over  the  naked 
fire.  The  temperature  to  be  obtained,  is,  however,  only  limited, 
but  by  a  proper  management  of  the  fire  any  degree  of  heat,  up  to 
the  maximum  amount  which  the  intermedium  is  capable  of  re- 
ceiving from  the  means  employed,  can  be  obtained. 

Baths  consist  of  two  vessels  of  different  diameters,  and  they  may 
be  either  of  metal,  stoneware,  or  porcelain.  The  outer  jacket 
receives  the  intermediary  body,  and  the  inner  one  the  substance 
to  be  heated.  As  generally  constructed,  baths  are  made  with 
but  one  jacket,  the  aperture  or  mouth  being  of  diameter  cor- 
responding with  that  of  the  heating  vessel  which  is  to  be  placed 
over  it.  This  arrangement  obviates  the  necessity  of  an  inner 
jacket,  and  also  of  the  transfer  of  the  substance  which  is  being 
heated. 

Baths  are  useful  in  operating  upon  organic  and  other  bodies 
easily  alterable  by  heat.  They  are  also  convenient  for  deter- 
mining the  melting-point  of  those  substances  which  are  fusible  at 
or  below  the  degree  of  heat  which  can  be  imparted  to  the  liquid 
or  vapor  of  the  bath :  that  temperature  being  made  known  by 
immersing  a  thermometer  at  the  commencement  of  the  fusion  and 
noting  the  degree. 

In  the  fluid  baths  the  thermometer  may  be  permanently  fixed 
by  means  of  *a  perforated  cork,  closing  a  circular  aperture  in  the 
lid.  Fig.  120,  with  the  scale  upon  the  stem,  exhibits  the  most 
suitable  form  of  the  instrument  for  this  purpose.  The  difference 
in  temperature  between  the  bath  and  the  heating  substance^ 
which  is  sometimes  very  considerable,  especially  when  porcelain 
or  glass  is  used,  may  be  diminished  by  keeping  the  bath  always 
covered.  If  the  vessels  have  smooth  surfaces,  the  heat  obtained 
previous  to  ebullition  is  much  higher  than  in  the  opposite  case. 
While  the  bath  is  in  use,  care  must  be  taken  that  the  amount  of 
the  liquid  in  the  outer  vessel  remains  as  nearly  as  possible  the 
same  throughout  the  process,  and  the  loss  from  evaporation  or 
exit  of  vapor  should  be  replaced  by  frequent  but  gradual  additions 
of  the  same  fluid. 

Steam-bath. — This  apparatus  forming  a  fixture  of  the  labora- 
tory has  been  fully  described  at  p.  46,  D  and  B,  Fig.  18,  and  is 
very  serviceable  in  extracting  vegetable  matters,  and  for  rapid 


' '  Vf 
266  STEAM-BATH — WATER-BATH. 


evaporations  at  temperatures  below  the  heat  of  direct  fire.  It  is 
also  a  convenient  arrangement  for  heating  those  substances  which 
would  be  alike  injured  by  direct  contact  with  steam.  It  affords 
a  temperature  of  fully  212°  F.  when  used  without  pressure  as  at 
D.  When,  however,  the  steam  is  employed  under  pressure,  as  is 
provided  for  in  B,  a  temperature  of  240°  F.  can  be  obtained  with 
ten  pounds  to  the  inch.  With  five  pounds  pressure  the  tempera- 
ture will  be  226°  F. 

For  very  small  operations,  the  apparatus  of  Dr.  Ure,  Fig.  198, 

is  an  excellent  contrivance.  "It 
Flg*  198'  consists  of  a  tin  box,  about  18 

inches  long  by  12  broad  and  6 
deep.  The  bottom  is  hollowed 
a  little  by  the  hammer  towards 
its  centre,  in  which  a  round  hole 
is  cut,  of  five  or  six  inches  in 
diameter.  Into  this  a  tin  tube, 
three  or  four  inches  long,  is  sol- 
dered. This  tube  is  made  to  fit 

tightly  into  the  mouth  of  a  common  tea-kettle,  which  has  a 
movable  handle.  The  top  of  the  box  has  a  number  of  circular 
holes  cut  in  it,  of  different  diameters,  into  which  evaporating  cap- 
sules of  platinum,  glass,  or  porcelain  are  placed.  When  the 
kettle,  filled  with  water  and  with  its  nozzle  corked,  is  set  on  a 
stove,  the  vapor  playing  on  the  bottom  of  the  capsules  heats  them 
to  any  required  temperature,  and  being  itself  continually  con- 
densed, it  runs  back  into  the  kettle  to  be  raised  again  in  cease- 
less cohobation.  With  a  shade  above  to  screen  the  vapor-chest 
from  soot,  the  kettle  may  be  placed  over  a  common  fire.  The 
orifices  not  in  use  are  closed  with  tin  lids.  In  drying  precipi- 
tates, the  tube  of  a  glass  funnel  may  be  corked  and  placed  with 
its  filter  directly  into  the  opening  of  a  proper  size.  For  drying 
red  cabbage,  violet  petals,  &c.,  a  tin  tray  is  provided,  which  fits 
close  to  the  top  of  the  box  within  the  rim  which  goes  about 
it.  The  round  orifices  are  left  open  when  this  tray  is  applied." 

Water-lath. — The  water-bath  is  used  for  heating  substances  at 
temperatures  within  that  of  boiling  water.  It  is  very  available 
where  bodies  easily  decomposable  by  high  temperatures  are  to  be. 


CONSTRUCTION    OF   WATER-BATH.  267 

heated,  and  is  also  useful  for  the  gradual  exhaustion  of  vegetable 
and  other  substances  which  only  give  up  their  soluble  matter  after 
long  contact  with  the  warm  solvent  liquid.  They  also  serve  to 
complete  evaporations  to  dryness,  which,  though  commenced  on 
the  sand-bath,  require  at  the  end  a  more  intense  heat.  Though 
seldom  employed  for  the  purpose  of  reducing  the  temperature 
very  low,  it  may,  by  proper  management,  be  made  to  yield  any 
intermediate  temperature  from  32°  to  212°  F. 

Every  water  and  liquid  bath,  whatever  its  form  and  the  pur- 
pose to  which  it  is  to  be  applied,  should  be  so  constructed  that 
the  vaporized  portions  can,  if  necessary,  be  confined  within  the 
vessel  and  prevented  from  escaping  by  other  outlets  than  the 
safety  valve.  As  proximity  of  the  escaping  vapor  might  be  in- 
jurious to  the  substance  under  process,  the  escape-pipe  should 
have  its  exit  six  or  eight  inches  distant  from  the  sides  of  the 
vessel. 

Any  two  vessels  of  different  diameters,  one  within  the  other, 
may  form  a  water-bath,  provided  the  intervening  space  at  the 
bottom  and  sides  is  sufficient  to  contain  the  requisite  amount 
of  water.  Straw  at  the  bottom  and  sides  is  an  excellent  means 
of  steadying  the  inner  vessel  and  preventing  direct  contact  of  its 
surface  with  the  more  highly  heated  bottom  of  the  outer  vessel,  a, 
result  which'would  cause  the  temperature  of  the  inner  vessel  to 
be  raised  above  that  of  the  surrounding  water. 

Fig.  199. 


A  regularly  constructed  water-bath  of  convenient  form  is  shown 
in  Fig.  199.     "A  is  a  vessel  containing  the  water,  a  the  inner 


268  CONSTRUCTION   OF   WATER-BATH. 

flange  for  the  support  of  the  evaporating  dish  B,  or  different  cir- 
cular rings  when  smaller  dishes  are  employed,  d  is  a  tube  fur- 
nished with  a  stop-cock  for  the  escape  of  the  steam,  which,  in 
some  cases,  requires  to  be  carried  still  farther  off  by  an  additional 
tube  attached  to  it.  The  whole  apparatus  may  be  heated  either 
by  a  gas  stove  or  on  a  charcoal  furnace.  The  water-bath  is  filled 
about  half  full  with  water.  It  will  be  seen  that  water-baths  with 
cover  act  more  on  the  principle  of  steam-baths  as  soon  as  the 
quantity  of  water  which  they  contain  is  small.  Care  must  be 
taken  always  to  replenish  the  evaporating  water  by  adding  fresh, 
otherwise  not  only  the  experiment  may  be  ruined,  but  the  bath 
itself  become  seriously  injured." 

Large  tin  cups  make  excellent  water-baths  for  flasks  and  tall 
vessels.  The  bottom  of  the  flasks  may  rest  upon  small  straw 
rings  which  prevent  contact  with  the  heated  tin,  and  serve  also  to 
steady  them.  The  holes  in  the  lid  for  the  protrusion  of  the  necks 
of  the  flasks  also  assist  in  this  latter  respect. 

A  very  convenient  little  bath  for  small  ope- 
rations, is  shown  in  Fig.  200.      It  consists  of 
a  copper  capsule  #,  with  a  ledge  around  its  in- 
terior circumference  as  a  rest  or  support  for  the 
vessel  to  be  heated.      In  order  that  it  may  be 
applicable  to  capsules  of  various  sizes,  its  top  is 
fitted  with  a  series  of  thick  flat  copper  rings, 
which  afford  the  power  of  decreasing  the  diameter  of  the  outer 
capsule  to  suit  that  of  the  vessel  to  be  heated. 

The  whole  diameter  of  the  outer  vessel  is  about  7  inches,  and 
when  all  the  rings  are  placed  upon  the  top  the  opening  in  the 
centre  is  about  1  inch,  but  by  withdrawing  one  at  a  time  the  size 
of  the  mouth  can  be  increased  gradually  from  1  to  6J  inches,  and 
adapted  to  any  vessel  of  intermediate  size.  It  would  be  well  to 
have  a  small  tube  projecting  from  the  side,  so  as  to  answer  at  the 
same  time  the  purpose  of  a  handle,  and  of  an  exit  pipe  for  the 
waste  vapor. 

This  apparatus,  as  is  seen  in  the  figure,  is  mounted  upon  a 
tripod  5,  a  convenient  support  when  the  small  spirit-lamp  is  used 
to  heat  the  water.  When  a  stronger  heat  is  required,  it  can  be 
detached  and  mounted  upon  a  larger  support,  and  placed  over 


SALINE    BATHS. 


269 


Fig.  201. 


Fig.  202. 


the  gas  or  Berzelius  lamp.     Fig.  201   represents  the  apparatus 
without  the  tripod  and  with  handles. 

A  porcelain  or  tin  plate  placed  upon 
the  top  of  this  bath  renders  it  very  con- 
venient for  drying  small  filters,  precipi- 
tates, &c.  By  increasing  the  circumfer- 
ence of  the  bath  so  that  it  may  have  a 
broad  top,  and  by  piercing  the  latter  with 
circular  holes  of  various  diameters,  we 
obtain  a  means  of  heating  several  capsules  of  different  sizes  at  the 
same  time. 

For  holding  test  tubes  in  upright  position,  either  in  sand  or 
water-bath,  a  support  of  the  form  shown  by 
Fig.  202  will  be  found  both  convenient  and 
serviceable. 

The  still,  Figs.  18,  25,  without  its  head, 
makes  an  excellent  water-bath  for  large 
operations. 

Saline  baths. — The  substitution  of  saline 
solutions  for  water  aifords  a  means  of  ob- 
taining temperatures  higher  than  the  boil- 
ing-point of  that  liquid.     This  kind  of  bath 
is   very  useful    for    digestions  and  many 
other  operations.     The  saturation  of  the 
water  with  salts  raises  its  point  of  ebulli- 
tion, but  in  practice  it  is  necessary  to  use  weaker  solutions,  other- 
wise the  evaporation  of  the  water  would  be  continually  causing 
the  deposition  of  the  salt  and  the  solidification  of  the  liquid  to 
the  great  inconvenience  of  the  experimenter. 

The  following  table  exhibits  the  boiling-points  of  the  saturated 
solution  of  the  salts  most  generally  employed  for  this  purpose. 


BOILING-POINTS  OF  SATURATED  SOLUTIONS, 


Alum, 

Muriate  of  ammonia, 
Oxalate  of  ammonia, 
Tartrate  of  ammonia, 
Chloride  of  barium, 
Nitrate  of  baryta, 
Acetate  of  copper, 


220° 

237 

218 

230 

220 

214 

214 


Sulphate  of  copper,  .  216° 

Acetate  of  lead,  .  .212 

Chloride  of  calcium,  .  355 

Sulphate  of  magnesia,  .  .      222 

Cream  of  tartar,       .  ,  214 

Chloride  of  sodium,  .  .      227 

Tartrate  of  potassa,         '•'*.'=•*        224 


270  METALLIC   AND    OIL   BATHS. 


Sulphate  of  soda,  .             .      213C 

Nitrate  lime,           ".  -  .             303 

Carbonate  of  potassa,  .             .      275 

Chloride  of  zinc,     . '  .              320 

Rochelle  salt,     .  .             .      246 

Sulphate  of  nickel,  .             235 

Chlorate  of  potassa,  .             .219 

Nitrate  of  potassa,  .  .             238 

Quadroxalate  of  potassa,  .      220 


Acetate  of  soda,       .:•?,   f  V- '3  256° 

Nitrate  of  soda,  '   •    ,.         .  249 

Biborate  of  soda,     .  ,.  222 

Carbonate  of  soda,         .  .  .  220 

Phosphate  of  soda, .  .  222 

Nitrate  of  strontia,    }'**-•*        .  224 

Sulphate  of  zinc,     .  ,^|  220 

Boracic  aaid,      .  .  .218 


Chloride  of  zinc  is  available  at  temperatures  below  320°  F.,  at 
which  degree  it  gives  off  fumes  of  chlorhydric  acid  and  becomes 
unsuitable  as  a  medium  for  the  communication  of  heat.  A  layer 
of  oil  retards  the  evaporation  of  the  water  and  promotes  the  ele- 
vation of  the  temperature  of  the  solution. 

The  selection  of  the  salt  for  the  bath  must  be  with  regard  to 
economy  and  the  nature  of  the  material  of  the  vessels.  Corrosive 
solutions  should  only  be  used  in  those  vessels  upon  which  they  are 
without  action.  The  construction  of  the  bath  is  similar  to  that 
shown  in  Fig.  199. 

Metallic  Baths. — These  baths  are  only  convenient  for  small 
operations,  because  of  the  difficulty  of  supporting  the  weight  of 
a  large  amount  of  metal,  and  of  keeping  the  heating  vessels  im- 
mersed in  it.  They  furnish  temperatures  higher  than  either  of 
the  preceding,  and  for  greater  safety  must  be  heated  in  cast-iron 
vessels  of  form  suitable  to  the  experiment. 

Mercury  would  be  a  convenient  menstruum,  if  it  was  lighter 
and  emitted,  when  highly  heated,  less  noxious  fumes.  On  these 
accounts  it  is  but  rarely  used,  and  only  in  test  tubes  for  heating 
still  smaller  tubes.  The  fusible  alloy,  composed  of  eight  parts 
of  bismuth,  five  of  lead,  and  three  of  tin,  forms  an  excellent 
metallic  bath.  It  melts  below  212°  F.,  and  affords  very  high 
temperatures,  for  though  it  oxidizes  upon  the  surface  as  its  tem- 
perature is  increased,  it  will  bear  a  white  heat  without  emitting 
vapors.  Tin  melting  at  441°  F.  and  lead  at  609°  F.,  are  both 
available  for  a  temperature  above  their  fusing-points. 

Oil  Baths. — Oils  in  ebullition  throw  off  a  very  disagreeable 
vapor,  but  are  otherwise  convenient  for  furnishing  temperatures 
corresponding  with  and  below  their  boiling-point.  Care  should 
be  taken  not  to  apply  heat  sufficient  for  their  decomposition. 
Even  at  low  temperatures  they  have  the  advantage  over  water, 


THE  MODE  OF  PRODUCING  LOW  TEMPERATURES.    271 

of  losing  less  by  evaporation  and  of  affording  facility  in  regula- 
ting the  temperature.  The  oil  should,  before  its  transfer  to  the 
bath,  be  heated  in  an  iron  capsule  for  several  hours,  to  expel 
moisture.  The  bath  consists  of  a  porcelain  lined  or  metallic 
jacket,  of  construction  exactly  similar  to  that  of  the  water-bath. 
It  affords  a  temperature  of  570°  F.  A  THERMOMETER  is  neces- 
sary for  noting  the  temperature  of  the  bath,  to  which  end  its 
bulb  must  be  kept  immersed  in  the  oil. 

Sand-bath. — This  bath  is  of  more  general  application  for  labo- 
ratory purposes  than  either  of  the  others.  Its  different  forms  and 
their  appropriate  uses  have  already  been  fully  described  at  pp.  30, 
33, 40,  66,  Figs.  9, 11}  17,  43.  Sand  is  used  because  it  is  a  better 
resistant  of  sudden  changes  of  temperature,  and  affords  a  uniform 
heat,  greater  or  less,  as  may  be  required,  than  that  of  the  water- 
baths.  Magnesia  and  ashes  are  sometimes  substituted,  but  they 
are  too  apt  to  be  driven  about  by  slight  currents  of  air ;  the 
former  is  only  used  as  a  bed  for  platinum  or  porcelain  crucibles, 
which  are  to  be  enclosed  in  Hessian  crucibles  and  ignited. 

A  sand-bath  may  be  readily  constructed  by  filling  an  iron  pot 
with  sand  and  placing  it  upon  the  charcoal  furnace,  Fig.  124,  or 
upon  the  top  of  the  stove  which  heats  the  apartment,  or  over  a 
gas  burner.  It  is  then  ready  to  receive  glass  or  porcelain  vessels 
in  which  the  processes  of  evaporation,  digestion,  or  distillation 
may  be  carried  on.  Care  must  be  observed,  in  heating  the  sand, 
not  to  let  it  exceed  the  required  degree,  for  otherwise  time  will 
be  lost  in  waiting  for  its  fall,  as  it  cools  very  slowly. 


CHAPTER  XIII. 

THE   MODE   OF   PRODUCING   LOW   TEMPERATURES. 

THERE  are  many  chemical  processes  requiring  the  application 
of  low  temperatures ;  and,  therefore,  it  is  a  duty  of  this  work  to 
teach  the  means  of  producing  cold  artificially.  It  is  accomplished 
by  means  of  freezing  mixtures,  which  are  formed  of  substances 


272  THE    MODE    OF    PRODUCING   LOW   TEMPERATURES. 

having  a  tendency  to  liquefy  in  water  or  other  fluid.  The  ab- 
sorption of  heat,  by  the  freezing  mixture,  from  the  body  under 
process,  produces  a  depression  of  temperature  in  the  latter,  vary- 
ing as  to  degree  with  the  nature  and  proportions  of  the  mixed 
ingredients.  This  depression  of  temperature  is  incident  to  the 
disaggregation  of  the  salt  or  other  matter,  and  its  transition 
from  the  solid  to  the  liquid  state.  The  heat  thus  transferred  is 
regarded  as  a  species  of  latent  heat  of  fusion  of  the  salt,  differing 
measurably  from  the  latent  heat  of  igneous  fusion,  and  has  been 
termed  by  Regnault  "the  latent  heat  of  solution  of  a  salt." 

Ice  and  salt,  for  example,  when  mixed  together,  produce  a  cold 
of  6°,  owing  to  the  rapid  melting  of  the  ice  and  the  subsequent 
solution  of  the  salt  in  the  cold  water:  the  depression  of  tempera- 
ture, in  this  instance,  being  due  both  to  the  latent  heat  of  solu- 
tion of  the  salt  and  the  latent  heat  of  fusion  of  the  ice. 

Freezing  or  cooling  mixtures  are  necessary  for  determining  the 
congealing  point  of  fluid  substances ;  and  for  this  purpose  they 
must  surround  the  vessels  containing  the  latter.  When  the  two 
have  remained  sufficiently  long  in  contact  to  produce  the  desired 
result,  the  temperature  of  the  fluid,  at  the  moment  of  transition, 
must  be  noted  by  a  thermometer,  which  should  be  placed  in  it  at 
the  commencement  of  the  experiment.  Another  thermometer 
must  be  simultaneously  placed  in  the  freezing  mixture,  to  give 
assurance  that  the  internal  and  external  temperature  are  uniform, 
otherwise  the  fluid  may  congeal  on  the  walls  of  the  containing 
vessel  before  the  interior  of  the  mass  has  fallen  to  the  proper 
temperature. 

The  ingredients  composing  them  should  be  previously  pulve- 
rized, and  then  mixed  together  without  unnecessary  delay. 

In  very  small  operations,  the  vessels  to  be  cooled  are  refrige- 
rated by  keeping  the  surfaces  moistened  with  ether,  which,  vola- 
tilizing rapidly,  abstracts  and  carries  off  a  large  amount  of  heat. 

Freezing  mixtures  afford  the  facility  of  making  ice  at  all  sea- 
sons ;  and  a  convenient  apparatus  for  this  purpose,  as  well  as  for 
cooling  bottles  and  similar  vessels,  is  the  so-called  "  Family  Ice- 
box," represented  by  the  annexed  drawings. 

It  is  composed  of  a  hollow  cylinder  c,  for  receiving  the  refri- 
gerating vessel  I,  containing  the  water  to  be  frozen.  Another 
cylindrical  vessel  A,  with  a  close  bottom,  sets  in  the  freezing 


THE  MODE  OF  PRODUCING  LOW  TEMPERATURES. 


273 


mixture,  and  being  fitted  with  suitable  projections,  and  turned  by 
the  winch-handle,  agitates  the  mixture,  and  maintains  a  thorough 
contact  of  the  refrigerating  body  with  the  inner  and  outer  vessels. 
If  the  hollow  vessel  be  filled  with  water,  the  latter  freezes  like 
the  surrounding  water.  The  space  I,  and  also  the  cover  D  of  the 

Fig.  203. 


inner  cylinder  A,  are  enveloped  with  raw  cotton,  which,  as  a  bad 
conductor,  intercepts  the  heat  of  the  circumambient  air.  The 
freezing  mixture  should  be  added  in  three  separate  portions,  to 
insure  its  maximum  efficiency,  and  the  resulting  liquid  from  each 
drawn  off  into  the  lower  vessel  v  through  a  lever-cock,  before 
the  application  of  the  succeeding  portion.  The  cold  water  flowing 
into  the  receiver  v  renders  the  latter  a  convenient  cooling  vessel 
for  liquids  contained  in  bottles.  Thirty  to  forty  minutes  suffice 
for  making  a  cylinder  of  ice. 

The  following  tables  by  Walker  and  Karsten  present  formulae 
for  a  variety  of  freezing  mixtures,  with  the  degree  of  cold  which 
they  produce,  severally,  annexed. 

18 


274 


FREEZING  MIXTURES. 


TABLE  I. Consisting  of  Frigorific  Mixtures,  composed  of  Ice,  with  Chemical  Salts 

and  Aoids. 

Thermometer  sinks. 

.     2  parts  1  rto_5c 

.     1      "      J 


Mixtures. 

f  Snow  or  pounded  ice, 
1  Muriate  of  soda, 

(  Snow  or  pounded  ice,  .     5 

•<  Muriate  of  soda,          .  .     2 

I  Muriate  of  ammonia,  .     1 

f  Snow  or  pounded  ice,  .  24 

J  Muriate  of  soda,         .  .10 

j  Muriate  of  ammonia,  .     5 

t  Nitrate  of  potash,        .  .     5 

f  Snow  or  pounded  ice,  .  12 

•I  Muriate  of  soda,         .  .     5 

(Nitrate  of  ammonia,  .  .     5 

f  Snow,        .    ;    *        ••  .     3 

1  Diluted  sulphuric  acid,*  .     2 

fSnow,        .     ..    .         .  .8 

|  Muriatic  acid  (concentrated),  5 


D 
I 

S^ 


to  —12° 


to  —18° 


to  —25° 


?From  +32°  to  —23° 
I  From  +32°  to—  27° 
|  From  +32°  to—  30° 
|  From  +32°  to  —40° 
I  From  -f  32°  to  —50° 
From  +32°  to —51° 


55 


59 


62 


72 


82 


83 


f  Snow,        ....     7 

1  Concentrated  nitrous  acid,  .     4 

f  Snow,        .''.-•    .  '  .;      .     4 

(  Muriate  of  lime,          .         .     5 

(Snow,        ....     2 

I  Crystallized  muriate  of  lime,  3 

(Snow,        .....     3 

(Potash,      ....     4 
N.B. — The  reason  for  the  omissions  in  the  last  column  of  this  table  is,  the  ther- 
mometer sinking  in  these  mixtures  to  the  degree  mentioned  in  the  preceding 
column,  and  never  lower,  whatever  may  be  the  temperature  of  the  materials  at 
mixing. 

TABLE  II.— Consisting  of  Frigorific  Mixtures,  having  the  power  of  generating  or 
creating  Cold,  without  the  aid  of  Ice,  sufficient  for  all  useful  and  philosophical 
purposes,  in  any  part  of  the  world  at  any  season. 

Degree  of  cold 
produced. 

40° 


Thermometer  sinks. 


5  parts. 


5 

16 

5 

5 

8 


[•  From  +  50°  to  +10° 


•  From  +50°  to  +4° 


Mixtures. 

(  Muriate  of  ammonia,  . 
•\  Nitrate  of  potash, 
I  Water,       . 
f  Muriate  of  ammonia, 
j  Nitrate  of  potash, 
j  Sulphate  of  soda, 
I  Water,       .         .         .         .16- 

f  Nitrate  of  ammonia,  .         .     1 

(Water,       ....     1 

f  Nitrate  of  ammonia,  .         .     1 
•I  Carbonate  of  soda,      .         .     1 

( Water,        .         .         .         .     1      «      J 

*  Strong  acid  2  parts;  water  or  snow  1  part,  by  weight. 


46 


j  From  +50°  to  +4°         .      46 


From  4-50°  to —7° 


FREEZING   MIXTURES. 


275 


|  From  -f  50°  to  —3°       .        53° 


Mixtures.  Thermometer  sinks. 

(  Sulphate  of  soda,  . 
(  Diluted  nitrous  acid,* 
f  Sulphate  of  soda,  . 
J  Muriate  of  ammonia, 
j  Nitrate  of  potash,  . 
I  Diluted  nitrous  acid,  . 
f  Sulphate  of  soda,  . 
•<  Nitrate  of  ammonia,  . 
I  Diluted  nitrous  acid,  . 
f  Phosphate  of  soda,  . 
1  Diluted  nitrous  acid,  . 
("  Phosphate  of  soda,  . 
X  Nitrate  of  ammonia,  . 
I  Diluted  nitrous  acid,  . 
f  Sulphate  of  soda,  . 
(.  Muriatic  acid,  .  . 
f  Sulphate  of  soda,  . 
(  Diluted  sulphuric  acid,f 

N.  B.  —  If  the  materials  are  mixed  at  a  warmer  temperature  than 
in  the  table,  the  efiect  will  be  proportionately  greater;  thus,  if  the 
of  these  mixtures  be  made  when  the  air  is  -f-  85°,  it  will  sink  the  . 


Degree  of  cold 
produced. 


3  parts. 

2      " 

6      " 

4 

2 

4 

6 

5 

4 

9 

4 

9 

6 

4 

8 

5 

5 

4 


60 


64 

62 

.        71 

50 

47 

that  expressed 
most  powerful 
thermometer  to 


TABLE  III.  —  Consisting  of  Frigorific  Mixtures  selected  from  the  foregoing  tables 
and  combined  so  as  to  increase  or  extend  Cold  to  the  extremest  degrees. 


[-From  +50°  to  —10° 

From  +50°  to  —14° 
I  From +50°  to —12° 

I  From +50°  to—  21° 

1  From  +50°  to  0° 
1  From  4  50°  to  4.  3° 


Thermometer  sinks. 


5  parts.  1 


>•  From  0°  to  —34° 


^Mixtures. 

f  Phosphate  of  soda,  . 
j  Nitrate  of  ammonia,  . 
I  Diluted  nitrous  acid,  . 
( Phosphate  of  soda,  . 
}  Nitrate  of  ammonia,  . 
I- Diluted  mixed  acids, . 
(  Snow,  .  .  . 
(  Diluted  nitrous  acid,  . 

SSnow,        ,"      '.*'''.' 
Diluted  sulphuric  acid, 
Diluted  nitrous  acid,  . 
(Snow,        ... 
I  Diluted  sulphuric  acid, 
f  Snow,        .    •     .    ,  ,  . 
\  Muriate  of  lime,          . 
(  Snow,        .  •      . :-      • 
(  Muriate  of  lime,         . 
fSnow,        ....     2 
(  Muriate  of  lime,         .         .     3 

*  Fuming  nitrous  acid,  2  parts  ;  water  1  part,  by  weight, 
t  Equal  weights  of  strong  acid  and  water. 


From  —34°  to  —50° 

From  0°  to  — 46°    . 

V  From  — 10°  to  — 56° 

j  From  —20°  to  —60° 

1  From  +20°  to  —48° 

From  4-10°  to  —54° 

From  —1 5°  to  —68° 


Degree  of  cold 
produced. 

34° 


16 

46 
46 

40 
68 
64 


276  FREEZING   MIXTURES. 

Mixtures.  Thermometer  sinks. 

5Snow'          ..-.     lpart'}FromO°to-660,  66° 

<  Crystallized  muriate  of  lime,     2 

JSnOW'  '         '    .     '      1     "     }  From -40°  to -73°,          33 

C  Crystallized  muriate  of  lime,     3 

Pn°W',        \     •'      M'          'in     «     }  From -68°  to -91°,          23 
c  Diluted  sulphuric  acid,         .  10^    u     J 

Remarks. — The  above  artificial  processes  for  the  production  of  cold  are  more 
effective  when  the  ingredients  are  first  cooled  by  immersion  in  other  freezing 
mixtures.  In  this  way  Mr.  Walker  succeeded  in  producing  a  cold  equal  to  100° 
below  the  zero  of  Fahrenheit,  or  132°  below  the  freezing-point  of  water. 

The  materials  in  the  first  column  are  to  be  cooled,  previously  to  mixing,  to  the 
temperature  required,  by  mixtures  taken  from  either  of  the  preceding  tables. 

The  following  table  by  Karsten,  shows  the  diminution  of  temperature  in  degrees 
Fah.,  where  1  pt.  of  salt  is  dissolved  in  4  pts.  water. 

Salts.  Degrees  of  cold. 

Nitrate  of  lead, 3'4° 

"             baryta, 3-8° 

Common  salt, 3'8° 

Sulphate  of  copper,    . 4-0° 

"             potassa, 5-2° 

"             zinc, 5-6° 

"             magnesia,                  8'1° 

Muriate  of  baryta,       .        . 8'1° 

Sulphate  of  soda, 14'6° 

Nitrate  of  soda, ..  17-0° 

"             potassa, 19-1° 

Chloride  of  potassium, 2T3° 

Nitrate  of  ammonia, 25*4° 

Muriate  of  ammonia, 2  7- 3° 

The  following  table,  also  by  Karsten,  shows  the  degrees  of  cold  produced  by 
dissolving  1  pt.  of  a  salt  in  4  pts.  of  a  saturated  solution  of  another  salt : — 

Salts.  Sat.  solution  of.                             Degrees  of  cold. 

Sal  ammoniac,     .         .  Common  salt,  .         .         .        .  15 1° 

"               .         .  Saltpetre,          .         .         .         .  22-7° 

Saltpetre,     ...  Sal  ammoniac,         .         .         .  17-5° 

"             ...  Common  salt, ....  16-9° 

"             ...  Nitrate  of  soda,        .         .         .  12-7° 

"             ...  «           baryta,      .         .         .  17-5° 

...  "           lead,         .         .         .  17-1° 

Glauber's  salt,     .         .  Common  salt,  .         .        .         .  8- 5° 

Common  salt,       .         .  Blue  vitriol,      ....  7*4° 

Nitrate  of  soda,    .         .  Sal  ammoniac,      v.  .    '     .        .  16-4° 

"         .        .  Saltpetre,          .   '„  ^  ,     .        .  16-6° 


FUSION.  277 


Salts. 

Sat.  solution  of. 

Degrees  of  cold. 

Nitrate  of  soda,    . 

Common  salt,  . 

. 

14-0° 

41                              (C 

Muriate  of  baryta,  . 

. 

14-9° 

(C                           U 

Nitrate  of  lead,     '  . 

. 

14-4° 

Nitrate  of  baryta, 

Saltpetre, 

. 

1-35° 

Sulphate  of  zinc, 

.;.>-.       Sulphate  of  potassa, 

. 

3-1° 

The  following  table,  by  Karsten,  of  1  pt.  salt  in  4  pts.  of  a  saturated  solution 
shows  an  increase  of  temperature : — 

Salts.  Sat.  solution  of.  Degrees  of  heat. 

Common  salt,       .         .         Sal  ammoniac,  .         .         .  8-2° 

"  "  Glauber's  salt,  .         •    «\          3'10 

"  "        Y/    '*        Saltpetre,         .'  '/*:    .     'V          1-35° 

"  "        ••;•        .-'      Nitrate  of  soda,  ,       '  f< •'/•<'      6-8° 

Muriate  of  baryta,         .  "  "  ...  1-15° 

By  mingling  solid  lead  amalgam  with  solid  bismuth  amalgam,  whereby  they 
become  liquid,  Orioli  obtained  39-6°  of  cold.  Dobereiner  mixed  204  pts.  lead 
amalgam  (103  lead  -f-  101  mercury)  with  172  pts.  bismuth  amalgam  (71  bismuth 
-|-  101  mercury),  and  obtained  a  diminution  of  from  68°  to  30-2°;  and  by  adding 
to  the  same  202  pts.  more  of  mercury,  the  temperature  fell  to  17-6.°  By  dissolving 
the  powders  of  59  pts.  tin.  103-5  pts.  lead,  and  182  pts.  bismuth,  in  808  pts.  mer- 
cury, the  thermometer  falls  from  63-5°  to  14°. 


CHAPTER  XIV. 

FUSION. 

THE  liquefaction  of  bodies  by  heat,  a  preliminary  step  to  many 
processes,  is  termed  fusion.  Igneous  fusion  applies  to  the  melting 
of  anhydrous  substances,  and  aqueous  fusion  to  the  liquefaction 
of  a  salt  in  its  water  of  crystallization. 

The  modes  of  performing  the  process,  and  the  material  and 
form  of  the  apparatus  employed,  vary  with  the  nature  of  the 
substance  to  be  acted  upon.  The  chief  point  to  be  attended  to  is 
the  selection  of  such  containing  vessels  as  are  not  injuriously 
affected  by  the  fused  substances, — and  which  do  not  themselves 
react  upon  their  contents. 

The  implements  for  fusion  are  called  crucibles,  the  smaller  of 
which,  for  the  less  refractory  substances,  may  be  heated  over  the 
GAS  or  SPIRIT  LAMP.  To  effect  the  liquefaction  of  bodies  diffi- 


278  CRUCIBLES. 

cultly  fusible,  or  of  large  quantities  of  matter,  a  FURNACE  is 
requisite. 

The  size  of  the  crucible  should  be  proportional  to  the  quantity 
of  matter  to  be  heated  in  it.  It  is  best  that  its  capacity  should 
be  no  greater  than  sufficient  for  the  contained  substance  with 
enough  margin  to  allow  for  swelling  or  foaming. 

CRUCIBLES. — A  crucible,  to  be  available  for  any  and  every 
operation,  should  possess  the  quality  of  compactness,  in  order  to 
resist  the  corrosive  action  of  fused  substances,  the  permeability 
of  gases  and  liquids,  the  fusing  power  of  intense  heat,  and  the 
tendency  to  fracture  by  sudden  changes  of  temperature. 

It  is  impossible  to  combine  all  these  requisites  in  any  one  kind 
of  crucible. 

The  materials  of  which  crucibles  are  formed  are  either  pure 
clay,  or  clay  mixed  with  charcoal,  quartz,  graphite,  or  coke,  to 
render  it  more  refractory.  Black  lead,  porcelain,  silver,  and  pla- 
tinum, have  each  and  all  their  appropriate  application. 

Clay  Crucible&.-r-The  Hessian  and  French  crucibles  are  those 

Fig.  204.  °f  tnis  description,  which  are  most  used.  The 
Hessian,  so  called  from  the  place  of  their  manu- 
facture in  Germany,  are  either  in  the  form  of 
a  tapering  cylinder  or  triangular,  and  are  that 
kind  of  crucible  most  commonly  found  in  our  drug 
shops.  They  are  met  with  in  nests  of  a  half  dozen 
or  more,  gradually  increasing  in  size  from  the 
smallest  (of  an  ounce)  to  the  largest,  of  pint  or  quart  capacity. 

They  are  grayish  yellow  or  whitish,  rough  to  the  touch,  and 
should  give  a  clear  ring  when  held  by  the  bottom  and  sounded  on 
the  sides.  Being  hard  and  impermeable,  they  are  very  useful 
for  rough  fusions ;  but  the  silica  which  they  contain  renders  them 
unfit  for  metallic  oxides,  with  which  at  high  heat  it  combines. 

The  Hessian  crucibles  require  careful  usage,  as  they  are  liable 
to  be  fractured  by  even  slight  changes  of  temperature.  There- 
fore, notwithstanding  their  great  cheapness,  the  London  or  French 
crucibles  are  more  preferable  for  nice  operations. 

The  Loridon  crucibles  are  very  refractory,  regularly  formed, 
with  smooth  surfaces,  and  will  endure  a  very  high  heat. 

The  French  crucibles,  Fig.  205,  which  are  manufactured  by 


•1 

PORCELAIN  CRUCIBLES.  279 

Beaufaye,  of  Paris,  are  said  to  be  far  superior  to  Fig.  205. 
either  of  the  preceding.  They  are  whitish,  well 
shaped,  and  smooth  throughout,  and  being  nearly 
free  from  oxide  of  iron,  and  less  rich  in  silica,  are 
applicable  for  the  fusion  of  nearly  all  substances 
except  certain  salts,  which,  owing  to  the  porosity  of 
the  crucible  material,  are  readily  absorbed. 

Being  capable  of  supporting  extreme  heat  as  well 
as  sudden  changes  of  temperature,  they  are  very  useful  for  the 
reduction  of  oxides  and  fusion  of  metals.     Borax,  glass,  and 
similar  substances,  remain  perfectly  colorless  when  melted  in 
these  crucibles. 

The  mixture  of  graphite  or  coke  with  the  clay,  which  is  found 
in  those  of  Austin's  make,  renders  them  capable  of  better  sup- 
porting the  softening  influence  of  the  wind  furnace  and  with- 
standing the  most  sudden  changes  of  temperature,  but  the  pro- 
portion of  the  latter  must  not  exceed  33  per  cent.,  otherwise 
its  combustion  by  the  fire  will  leave  the  crucible  porous  and 
fragile. 

As  metallic  oxides  are  reducible  when  hot,  by  contact  with 
carbonaceous  matter,  these  crucibles,  when  used  for  heating  those 
substances,  should  be  lined  with  a  thick  coat  of  clay  paste  and 
dried. 

Charcoal  is  the  only  proper  fuel  for  earthen  crucibles,  as  coke 
is  apt  to  form  scoriae,  which  attach  to  the  crucible  and  impede 
the  draught. 

Black  Lead  Crucibles.  Blue  Pots. — Black  lead  or  plumbago, 
when  mixed  with  one-fourth  of  its  weight  of  refractory  clay, 
becomes  capable  of  supporting  intense  heat  and  sudden  changes 
of  temperature.  The  chief  use  of  crucibles  made  of  this  sub- 
stance is  in  metallurgy,  for  the  purposes  of  which  their  smooth 
surface  admirably  adapts  them.  They  are  not  sufficiently  com- 
pact for  the  fusion  of  salts. 

Porcelain  Crucibles. — Crucibles  of  this  material  are  very  neat 
implements,  but  by  reason  of  their  incapability  of  resisting  even 
slight  changes  of  temperature,  are  only  used  for  purposes  to  which 
those  of  more  refractory  material  are  for  other  reasons  not 
adapted.  For  heating  over  the  lamp  they  must  be  small  and 
thin.  In  analytic  and  nice  operations  they  replace  platinum  in 


280 


PORCELAIN  CRUCIBLES. 


many  processes  in  which  the  contents  act  upon  that  metal,  for 
example,  in  igniting  plumbic  precipitates,  melting  metallic  oxides 
with  sulphobases,  preparing  enamels,  and  heating  metallic  oxides, 
which  are  reduced  easily  in  contact  with  platinum. 

The  crucibles,  Figs.  206,  207,  used  directly  over  the  lamp, 
should  never  exceed  an  ounce  or  two  in 
capacity,  for  even  with  the  most  careful 
management  it  will  be  difficult  to  cool 
one  of  larger  size  gradually  enough  to 
prevent  its  breaking.  Berzelius  recom- 
mends their  insertion  in  platinum  cru- 
cibles as  a  means  of  diminishing  their 
fragility.  The  French  porcelain  being 
very  thin  and  light,  and  a  better  supporter  of  sudden  changes  of 
heat,  is  preferable  to  the  Berlin  for  small  crucibles. 

The  impermeability  and  cleanliness  of  these  crucibles,  render 
them  very  convenient  for  the  fusion  of  certain  nice  substances, 
such  as  nitrate  of  silver,  potassa,  &c.,  in  large  quantities,  and  as 
it  is  impracticable  to  have  a  very  large  platinum  crucible  in 
private  laboratories,  one  of  porcelain  is  substituted.  These  large 
crucibles,  made  with  covers,  may  be  of  either  of  the  forms,  Figs. 
208,  209,  210,  and  of  Berlin  porcelain,  which  is  similar  to  Wedg- 
wood-ware, and  heavier  and  cheaper  than  the  French. 


Fig.  208. 


Fig.  209. 


Fig.  210. 


Fig.  211. 


The  large  crucibles,  varying  in  size  from  two  to  six  inches  in 
height,  and  from  one  to  four  inches  in  diameter,  may  be  entirely 
biscuit,  or  else  glazed  only  internally,  and  if  heated  over  the  fire 
require  to  be  enclosed  in  a  refractory  fire-clay  case,  as  shown  in 
Fig.  211.  This  case  is  equally  useful  for  platinum  or  silver  cru- 
cibles (Figs.  214,  215),  as  it  gives  them  a  proper  elevation  above 
the  grate,  and  prevents  contact  with  the  coals. 


IRON  AND   SILVER   CRUCIBLES.  281 

For  the  heating  of  more  readily  fusible  substances  they  may 
be  imbedded  in  a  sand-bath  and  heated  up  gradually.  If  allowed 
to  remain  in  the  bath  until  it  has  cooled,  the  liability  of  fracture 
from  sudden  refrigeration  will  be  diminished. 

Some  of  the  crucibles  have  duplicate  covers,  one  of  which  is 
perforated  and  used  to  facilitate  the  escape  of  the  gaseous  matter 
generated  during  certain  processes. 

Metallic  Crucibles. — Cast  and  plate  iron,  silver,  and  platinum, 
are  all  used  as  materials  for  crucibles. 

Iron  Crucibles. — For  the  fusion  of  silicates  and  certain  sele- 
niurets,  sulphurets,  and  other  substances,  iron  crucibles  are  very 
convenient.  An  exterior  coating  of  clay  is  requisite  to  protect 
them  from  the  oxidizing  action  of  the  air,  to  which  they  are  sub- 
jected at  high  temperatures.  The  same  object  may  be  effected 
by  inserting  them  in  clay  crucibles.  When,  however,  the  heating 
is  not  of  long  duration  nor  intense,  they  may  be  used  naked. 

Those  of  wrought  iron,  Fig.  212,  are  struck  up  from  a  single 
piece  of  thick  sheet  metal. 

Fig.  212.  Fig.  213. 


Cast-iron  crucibles,  Fig.  213,  are  cheaper,  and  equally  as  good 
as  wrought  iron  for  medium  temperatures,  but  they  must  be 
turned  smooth  interiorly. 

As  some  of  the  constituents  of  stove  coal  exert  a  chemical 
action  upon  metal,  the  only  proper  fuel  is  charcoal,  when  furnaces 
are  used  for  heating  the  crucibles. 

Silver  Crucibles. — Silver  crucibles  are  but  rarely  used,  save 
for  the  fusion  of  potassa,  soda,  and  for  the  preparation  of  caustic 
baryta  from  the  nitrate.  For  most  operations  they  are  well 
replaced  by  platinum.  For  acid  substances  their  use  is  improper. 
The  spirit  or  gas  lamp  is  the  heating  apparatus,  but  the  heat  must 


282  PLATINUM  CRUCIBLES. 

not  be  too  high  nor  of  too  long  duration,  for  the  silver  is  apt  to 
become  brittle  in  spots  as  it  assumes  a  crystalline  form  under  the 
influence  of  long-continued  red  heat. 

Platinum  Crucibles. — Platinum  crucibles  are  of  more  general 
application  than  those  of  any  other  material.  They  are  very 
tough  and  infusible  at  any  heat  that  can  be  obtained  from  the 
gas  or  spirit  lamp,  the  almost  exclusive  means  employed  for  that 
purpose.  As  they  are  liable  to  become  rough  at  high  furnace 
temperatures,  they  should,  when  exposed  to  such  influences,  be 
inserted  in  an  earthen  crucible,  and  surrounded  by  a  bed  of 
magnesia. 

Their  strong  resistance  to  the  action  of  chemical  reagents  ren- 
p.y  214  ders  them  indispensable  in  many  opera- 

tions, which  it  would  be  difficult  other- 
wise to  perform.  They  vary  in  size 
from  a  fluid-drachm  to  three  or  more 

_i L  fluid  ounces  capacity,  the  latter  being 

as  large  as  is  necessary  for  any  purpose 
in  a  private  laboratory.  Their  form  is  shown  in  Figs.  214,  215. 
The  crucibles  intended  to  be  heated  over  the  lamp  must  be  of 
very  thin  metal,  so  that  they  can  be  weighed,  as  is  often  neces- 
sary, in  a  delicate  balance.  To  give  strength,  however,  the 
bottom  must  be  thicker  than  the  sides.  Two  of  the  smaller 
size  will  be  found  more  useful  than  one  of  the  larger.  In  analysis 
a  half  ounce  crucible  is  indispensable  for  the  IGNITION  of  filters. 
The  cover  is,  as  seen  in  the  figure,  slightly  convex  exteriorly, 
and  ledged  around  the  circumference :  this  form  is  convenient 
when  the  vessel  is  to  be  entirely  closed  when  heated ;  but  in  cer- 
tain operations  in  the  wet  way  it  is  reversed,  so  that  the  convex 
side  may  rest  inwardly  and  return  any  particles  of  its  contents 
that  may  be  projected  upwards,  by  a  too  sudden  or  intense  eleva- 
tion of  temperature.  The  pin  running  through  its  centre  is  the 
knob  by  which  it  is  handled,  when  cold  with  the  fingers,  and  when 
hot  with  the  tongs,  Figs.  149, 150. 

Platinum  crucibles  are  also  made  with  covers,  in  the  shape  of 
capsules,  as  shown  by  Fig.  215.  They  are  very  convenient  for 
small  evaporations,  and  are  at  the  same  time  made  to  fit  closely 
or  loosely  to  the  body  of  the  crucible,  as  may  be  desired. 

Unless  the  crucibles  are  made  of  perfectly  pure  metal,  and  are 


THE   CONSTRUCTION   OF  CRUCIBLES.  283 

hammered  out  instead  of  being  turned,  their  F.    215 

power  of  enduring  strong  heats  and  resisting 
the  action  of  chemical  reagents  will  be  im- 
paired. The  blisters  and  flaws  which  appear, 
after  use,  are  owing  to  impurity  and  bad  work- 
manship, and  are  to  be  removed  by  the  force 
of  a  small  hammer. 

When  the  crucible  becomes  cracked  or  per- 
forated, it  can  be  repaired  by  welding  on  a 
layer  of  platinum  sponge,  but  it  is  far  better 
to  have  it  melted  up  and  remodelled  by  a  manufacturer. 

Boiling  or  hot  water  loosens  adherent  saline  matters,  and  fused 
borax  or  muriatic  acid  will  remove  all  stains  which  do  not  disap- 
pear by  rubbing  with  sand  or  pumice-stone.  The  use  of  sharp- 
pointed  instruments  will  be  apt  to  injure  the  crucible. 

The  experimenter  himself  can,  in  any  emergency,  readily  form 
a  crucible  out  of  platinum  foil  by  shaping  it  with  the  thumb  or  a 
small  hammer,  in  a  hemispherical  cavity  made  for  the  purpose, 
in  a  wooden  block. 

Berzelius  ( Traite  de  Chimie,  vol.  viii)  gives  the  following  in- 
structions as  to  the  manner  of  using  platinum  crucibles. 

"  Dry  fusion  should  never  be  effected  in  platinum  crucibles  : 
1st.  Caustic  'alkalies,  nitrates  of  lime,  baryta,  or  strontia,  and 
alkaline  nitrates,  always  attack  the  platinum.  Alkaline  sulphu- 
rets  or  sulphates  with  charcoal  are  still  more  injurious.  Metals, 
when  heated  to  their  melting-points,  alloy  with  it,  and  hence 
lead,  tin,  antimony,  &c.,  should  never  be  even  moderately  heated 
in  it.  Even  their  oxides,  especially  those  of  copper,  lead,  bis- 
muth, and  nickel,  reduce  at  a  high  heat  by  contact  with  platinum, 
particularly  if  charcoal  is  present,  the  two  former  at  a  lower 
temperature  than  the  latter.  Gold,  silver,  copper,  and  others, 
can  be  reddened,  but  not  melted  in  platinum.  Phosphorus  or 
phosphoric  acid  and  carbon  readily  attack  it.  Sulphate  of  lead 
may  be  burned  off  in  it  with  care,  but  for  the  chloride,  porcelain 
should  be  used. 

"  Silica  may  be  ignited  in  platinum,  but  it  combines  with  sili- 
cium  at  a  heat  beyond  redness,  and  therefore  they  should  always 
be  encased  when  heated  in  the  fire,  otherwise,  if  in  contact,  it 
will  abstract  it  from  the  coals. 


284  DIRECTIONS   FOR  HEATING   CRUCIBLES. 

"  Nearly  all  liquids  may  be  heated  in  platinum,  except  they 
contain  chlorine,  bromine,  iodine,  or  nitro-muriatic  acid. 

"  For  the  fixed  alkalies,  gold  is  preferable  to  either  silver  or 
platinum,  upon  which  they  have  a  more  or  less  corrosive  action." 

Directions  for  Heating  Crucibles. — All  the  larger  and  coarser 
crucibles  are  heated  in  FURNACES.  Their  proper  position  is  an 
upright  one  in  the  centre  of  the  grate,  upon  a  slight  elevation. 
They  should  be  warmed  before  being  placed  in  the  furnace,  so  as 
to  prevent  liability  to  crack  by  sudden  heating.  Ignited  coals 
are  then  placed  at  the  bottom  of  the  grate  and  covered  with  al- 
ternate layers  of  unlit  coke  and  charcoal,  of  nut  size,  until  the 
crucible  is  surrounded  up  to  the  level  of  its  top  with  fuel.  When 
the  crucible  is  to  be  strongly  heated,  it  should  be  covered  and  the 
fuel  heaped  over  its  top.  In  all  cases  the  fire  must  be  gradually 
raised  and  steadily  kept  up,  and  the  furnace  only  opened  when 
fresh  additions  of  coal  are  necessary,  as  it  is  important  that  there 
shall  be  no  variation  of  temperature  in  its  interior.  The  dura- 
tion of  the  process,  and  the  degree  of  heat  employed,  must  de- 
pend upon  the  nature  of  the  substance  under  process. 

After  the  completion  of  the  operation,  the  crucible  should  be 
allowed  to  cool  with  the  furnace,  or  if  taken  out  immediately, 
placed  upon  a  brick  or  bed  of  warm  sand,  otherwise  a  too  sudden 
change  of  temperature  will  cause  its  fracture.  The  furnace 
tongs,  Fig.  148,  are  conveniently  shaped  for  this  purpose. 

As  it  is  occasionally  necessary  to  poke  the  fire  in  order  that 
the  fuel  may  settle  previous  to  fresh  additions,  it  will  be  well  to 
give  the  crucible  a  firm  position  upon  a  stand  for  the  purpose, — 
the  half  of  a  fire-brick,  for  instance,  so  that  in  the  settling  of  the 
coal,  there  may  be  no  risk  of  its  being  upset.  When  by  intense 
heat  its  bottom  has  become  welded  to  the  brick,  the  latter  can 
very  readily  be  detached  by  a  gentle  tap  of  the  poker. 

Most  of  the  common  crucibles  serve  only  for  a  single  ope- 
ration. 

Covers  may  be  made  by  inverting  a  smaller  crucible  over  the 
top;  or  better,  by  making  a  dough  of  Stourbridge  clay,  and 
luting  it  on.  The  crucible,  in  the  latter  case,  must  not  be  heated 
until  the  cover  has  dried.  These  lids  have  a  tendency  to  retard 
volatilization,  and  are  necessary  to  prevent  the  entrance  of  fall- 
ing particles  of  coal  and  ashes.  For  the  escape  of  gaseous 


FUSION  OF   SUBSTANCES   UNALTERABLE  BY  HEAT  OR  AIR.      285 

matter  a  small  perforation  in  the  centre  of  the  cover  is  necessary, 
but  in  intensely  hot  fusions  all  other  openings  must  be  closed  with 

LUTE. 

The  smaller  metallic  crucibles  are  almost  exclusively  heated 
over  LAMPS.  They  are  supported  upon  wrought  iron  rings, 
Figs.  179,  180,  the  diameter  of  which  may  be  reduced  when 
necessary,  by  the  use  of  the  wire  triangles,  Fig.  181,  of  the  re- 
quired size. 

If  the  crucibles  are  very  small  they  may  be  heated  by  the 
mouth  blow-pipe.  For  the  larger  an  Argand,  spirit,  or  gas  lamp, 
Fig.  165,  is  needed.  To  hasten  the  process  or  to  increase  the 
temperature,  the  table  blow-pipe,  Figs.  45, 164,  is  convenient,  as 
it  gives  a  powerful  blast. 

The  use  of  the  jacket,  Fig.  156,  is  an  additional  means  of  still 
further  economizing  and  increasing  the  power  of  the  flame.  It 
also  diminishes  the  loss  of  heat  from  the  crucible  by  radiation, 
especially  when  the  latter  is  covered.  In  charging  the  crucibles, 
the  contents  should  be  concentrated  into  as  small  a  space  as  pos- 
sible, and  any  adherent  particles  should  be  brushed  from  the 
sides  with  a  feather.  When  the  crucibles  are  emptied  of  their 
fused  contents,  the  melted  matter  may  be  made  to  flow  upon  a 
smooth  and  clean  slab  of  marble,  iron,  or  other  proper  material, 
— great  care  being  taken  that  it  does  not  come  in  contact  with 
any  moisture  or  damp  substance. 

Fusion  of  Substances  unalterable  by  Heat  or  Air. — This  class 
comprises  a  very  large  number  of  substances,  among  which  are 
the  noble  metals,  &c.  The  crucible  employed  should  be  kept 
covered  as  well  whilst  cooling  as  heating,  and  the  refrigeration 
must  be  gradual,  or  the  molten  matter  may  spirt.  There  are 
other  metals  again,  for  instance,  zinc,  lead,  tin,  antimony,  and 
bismuth,  which,  at  high  temperatures,  oxidize 'readily  upon  ex- 
posure. In  such  cases  it  is  well,  in  addition  to  keeping  the 
vessel  closed,  to  cover  the  fluid  mass  with  a  layer  of  powdered 
charcoal. 

When  a  metal  is  in  process  of  fusion  it  is  imprudent  to  make 
fresh  additions  without  having  first  heated  the  material  to  be 
added,  for  the  sudden  entrance  of  cold  or  damp  matter  into  the 
hot  fluid  mass  will  cause  the  ejection  of  particles,  and  perhaps 
serious  inconvenience. 


286      FUSION  OF   SUBSTANCES   ALTERABLE   BY  HEAT   OR  AIR. 

In  the  manufacture  of  alloys  the  metals  should  be  well  incor- 
porated by  occasional  stirring.  When  iron,  and  indeed  manga- 
nese, cobalt,  nickel,  and  chrome,  are  being  exposed  to  high  degrees 
of  heat,  the  crucibles  must  be  free  from  carbonaceous  matter, 
otherwise  a  combination  may  ensue  at  high  temperatures. 

Fusion  of  Substances  alterable  by  Heat. — For  the  treatment 
of  substances  which  melt  below  212°  F.,  the  water-bath  is  conve- 
nient. The  fusion  of  substances,  such  as  wax,  resin,  and  fat, 
immiscible  with  that  liquid,  may  be  facilitated  by  the  direct  ap- 
plication of  boiling  water,  as  they  can  be  readily  removed  from 
the  surface,  to  which  they  rise,  with  a  ladle  or  syphon  whilst  hot, 
or  in  a  mass  if  allowed  to  cool. 

Substances  requiring  a  temperature  at  or  below  550°  for  their 
fusion,  may  be  melted  in  an  oil-bath. 

Alloys  containing  volatile  metals  should  be  heated  as  quickly 
as  possible. 

Certain  substances  which  volatilize  at  low  temperatures  re- 
quire to  be  fused  in  closed  vessels.  Iodine  and  arsenic  are 
examples. 

A  tube  of  glass,  porcelain,  or  metal,  according  to  the  nature 
of  the  substance,  is  the  best  form  of  apparatus  for  this  purpose. 
It  should  be  rounded  at  one  end,  and  after  the  introduction  of 
the  substance,  closed  at  the  other  over  the  blow-pipe.  The  tube 
must  be  heated  throughout  its  length. 

Fusion  of  Bodies  alterable  by  Air. — This  class  of  substances 
is  melted  in  seclusion,  the  air  being  shut  out  by  means  of  an 
intermedium  of  liquid,  powder,  or  fusible  matter.  Thus  potas- 
sium is  liquefied  under  naphtha,  phosphorus  under  water,  and 
certain  other  substances  in  powdered  charcoal. 

The  covers  of  the  crucibles  in  these  cases  must  be  tightly  luted, 
so  that  all  openings  may  be  closed. 

Fusion  of  difficultly  fusible  Substances. — All  substances  which 
resist  the  fusing  power  of  furnaces,  are  to  be  subjected  to  the 
more  intense  action  of  the  HYDRO-OXYGEN  BLOW-PIPE,  or  Bun- 
sen's  battery.  One  or  other  of  these  latter  means  will  prove 
effective,  in  all  possible  cases. 

Fusing-points. — The  usual  mode  of  determining  the  point  at 
which  a  substance  fuses,  is  to  place  a  thermometer  in  it  whilst 
fluid,  and  note  the  degree  at  which  solidification  ensues.  There 


IGNITION   OF   FILTERS.  287 

are,  however,  according  to  Brodie  (Mechanic's  Magazine,  1854), 
some  substances  whose  points  of  fusion  so  closely  approximate 
the  degree  at  which  they  assume  allatropic  conditions,  that  they 
require  a  modification  of  the  above  plan,  for  such  change  of  state 
is  always  accompanied  with  evolution  or  absorption  of  heat.  In 
these  cases  the  substance  is  to  be  divided  into  small  particles, 
placed  in  a  thin  glass  tube,  when  its  melting-point  is  below  that 
of  glass,  and  immersed  in  a  bath  of  boiling  dilute  sulphuric  acid 
or  other  suitable  liquid.  At  the  moment  the  contents  of  the  tube 
melts,  the  temperature  of  the  bath  is  to  be  noted  by  a  thermo- 
meter, and  recorded  as  the  fusing-point  of  the  substance  under 
experiment. 


CHAPTER  XV. 

IGNITION. 

SUBSTANCES  frequently  require  to  be  ignited  to  redness,  either 
as  the  sole  process  of  their  preparation,  or  as  a  preliminary  step 
to  subsequent  operations. 

Ignition  of  Filters. — In  analyses,  the  filters  containing  the  in- 
soluble or  precipitated  substances  which  are  to  be  estimated  are 
ignited  or  "burned  off,"  to  expel  carbonaceous  and  volatile 
matters  before  being  weighed.  The  implements  for  this  purpose 
are  porcelain  or  platinum  crucibles,  either  having  their  appro- 
priate applications. 

As  it  is  necessary  that  the  filter  should  be  wholly  or  partially 
dry,  it  must  be  carefully  removed  from  the  funnel,  so  as  not  to 
lose  a  particle  of  its  contents,  compressed  between  the  folds  of 
bibulous  paper,  and,  further,  dried  in  a  capsule  over  a  sand  or 
water  bath,  or  in  a  drying  stove  (DESICCATION),  at  a  temperature 
of  about  200°  F.  or  less.  The  dried  filter  and  contents  are  then 
to  be  transferred  to  the  crucible,  which  must  be  previously  weighed. 
The  transfer  must  be  made  without  the  loss  of  the  least  particle, 
and  for  this  purpose  the  crucible  may  be  placed  upon  a  sheet  of 
glazed  white  paper,  so  that  any  particles  that  accidentally  fall  in 
the  act  of  emptying  the  filter  may  be  preserved.  The  filter, 
after  having  been  freed  as  much  as  possible  from  the  adherent 


288  IGNITION  OF  FILTERS. 

precipitate  by  gently  rubbing  the  sides  together  between  the 
thumb  and  forefinger,  is  finally  placed  in  the  crucible  with  its 
contents — being  folded  loosely  and  laid  at  the  top.  The  force  used 
for  this  purpose  must  not  be  sufficient  to  abrade  the  paper,  other- 
wise the  matter  will  reach  the  fingers,  and  a  loss  thus  be  occa- 
sioned by  adherence.     The  crucible  is  then  heated  cautiously  and 
gradually  over  the  spirit  or  gas  lamp,  Fig.  141,  the  flame  of 
which  may  be  urged  by  the  blast.     For  the  first  few  moments  the 
vessel  should  remain  covered,  for  fear  of  loss  by  decrepitation,  but 
as  soon  as  it  becomes  red  hot  the  lid  may  be  wholly  or  partially 
removed,  and  the  crucible  inclined,  as  at  Fig.  216.     This  position 
promotes  free  draught  and  the  complete  and  rapid 
Fig.  216.         incineration  of  the  filter.  This  being  done,  the  cover 
is  replaced,  the  crucible  allowed  to  cool,  and  then 
weighed.     The  weight  of  the  crucible  and  that  of 
the  ashes  of  the  filter,  which  latter  has  been  pre- 
viously determined  by  the  incineration  of  filters  of  different  sizes, 
deducted  from  the  total  weight,  gives  the  weight  of  the  ignited 
precipitate. 

The  above  directions  apply  to  precipitates  which  are  not  alter- 
able by  being  burned  with  the  filter.  When,  however,  the  matter 
is  preserved  free  of  ashes  for  use  or  further  examination,  or  is 
liable  to  be  reduced  or  otherwise  changed  by  the  carbon  of  the 
filter,  the  latter  and  its  contents  must  be  ignited  separately.  In 

Fig.  217. 


such  cases,  the  drying  of  the  filter  and  the  detaching  of  its  con- 
tents are  accomplished  as  already  explained.     The  contents  are 


IGNITION   OF  FILTERS.  289 

heated  in  a  platinum  crucible  as  usual,  but  the  empty  filter,  after 
having  been  freed  as  much  as  possible  from  adhering  particles  of 
the  dry  contents,  is  incinerated  in  another  way,  originally  sug- 
gested by  Bunsen.  The  necessary  manipulation  consists  in 
placing  the  filter  upon  a  sheet  of  white  paper,  doubling  over  its 
circumference  first  at  the  sides  and  then  at  the  ends,  so  as  to 
guard  against  the  possibility  of  any  loss  of  matter,  and  finally 
rolling  it  up  into  a  tight  cylinder.  This  cylinder  is  next 
tightly  wrapped  with  one  end  of  a  platinum  wire,  and  held  over 
the  flame  of  an  alcohol  lamp,  as  shown  by  the  drawing,  until  the 
filter  has  become  thoroughly  incinerated.  The  original  volume 
of  the  filter  having,  of  course,  largely  contracted,  from  loss  of 
matter  by  the  heating,  it  will  easily  fall  from  its  position  in  the 
platinum  wire-coil  holder,  when  the  latter  is  held  over  the  crucible 
or  its  capsule  cover,  accordingly  as  it  may  be  desirable  to  weigh 
the  filter  ash  portion  and  the  pure  precipitate  jointly  or  sepa- 
rately. 

The  greatest  possible  care  must  be  observed  in  analytical  ex- 
periments to  prevent  the  least  loss  of  the  precipitate.  The  cru- 
cible must,  moreover,  in  all  cases,  be  cooled  under  a  bell  wherein 
is  a  vessel  containing  some  hygroscopic  substance,  so  as  to  pro- 
vide against  error  from  absorption  of  moisture  previous  to  the 
weighing. 

When  substances  are  to  be  ignited  for  the  determination  of 
their  hygroscopic,  volatile,  or  organic  matter,  heat  should  be  very 
gradually  applied,  without  the  blast,  and  to  a  limited  degree.  In 
these  instances,  the  crucible  should  be  weighed  first,  so  that  the 
loss  sustained  by  a  given  weight  of  its  contents,  during  ignition, 
may  be  ascertained  in  one  weighing,  merely  by  subtracting  the 
weight  of  the  crucible  and  contents  after  ignition  from  the  com- 
bined weight  of  the  two  before  the  same  process.  The  loss  gives 
the  amount  of  volatile  matter. 

In  analyses  of  coals,  the  moisture  can  be  determined  by  heat- 
ing the  crucible  in  a  hot  sand-bath,  or  very  gently  over  a  low 
flame.  After  the  loss  thus  occasioned  is  determined  by  weighing, 
the  amount  of  carbon  may  be  ascertained  by  subjecting  the  cru- 
cible and  contents  to  a  much  higher  heat. 

When  substances  are  to  be  exposed  to  heat,  the  crucible  and 
contents  must  likewise  be  weighed  separately  before  ignition. 


290  IGNITION  WITH  FLUXES. 

The  loss  of  weigtit  gives  the  amount  of  volatile  matter  driven-  off. 
The  ignited  matter  can  then  be  removed  from  the  crucible  by  hot 
•water  alone  or  acidulated. 

Scoriae  may  be  removed  from  platinum  crucibles-  by  covering 
them  with  a  paste  of  borax  and  carbonate  of  soda,  heating  them 
to  redness,  and  when  cold,  dissolving  out  the  saline  matter  with 
boiling  water.  A  repetition  of  the  process  is  necessary  to 
brighten  the  crucible  perfectly  if  it  had  been  very  dirty. 

Ignition  of  Bodies  in  Vapors. — If  it  be  desired  to  heat  a  fixed, 
substance  in  the  vapor  of  any  body,  which  is  solid  or  liquid  at 
ordinary  temperatures,  the  latter  may  be  put  into  a  tube  closed 
at  one  end,  or  into  a  small  flask  with  a  long  neck,  and  then  be 
heated  until  it  is  wholly  vaporized.  The  substance  is  to  be 
introduced  into  the  tube,  and  heated  in  the  vapor  at  any  desired 
temperature.  Thus,  to  show  the  affinity  of  sulphur  for  copper, 
the  former  is  heated  until  its  vapor  fills  the  whole  flask,  when 
slips  of  copper  foil  let  down  into  it  immediately  ignite  on  com- 
bining with  the  sulphur.  When  a  tube  is  used  it  may  be  held  in 
any  inclined  position,  but  a  flask  should  be  nearly  vertical. 

Ignition  with  Fluxes. — Fluxes  are  certain  substances,  usually 
saline,  mixed  with  other  bodies  in  order  to  promote  their  fusion 
or  decomposition  by  heat,  and  to  render  them  more  soluble  in 
water  and  acids.  All  ignitions  with  fluxes  in  experimental  ope- 
rations are  performed  in  crucibles  over  the  spirit-lamp  or  furnace 
fire,  and  for  the  fluxions  of  those  substances  in  which  there  is  no 
reducible  metallic  oxide,  platinum  is  by  far  the  best  material. 

The  process  is  particularly  useful  in  analysis  of  the  sulphurets, 
of  alkaline  earths,  of  many  silicates,  and  other  obstinate  com- 
pounds, and  also  in  metallic  operations. 

The  principal  objects  of  fluxing  are : — 

"  1.  To  cause  the  fusion  of  a  body,  either  difficultly  fusible,  or 
infusible  by  itself. 

"  2.  To  fuse  foreign  substances  mixed  with  a  metal,  in  order  to 
separate  the  latter  by  its  difference  of  specific  gravity. 

"  3.  To  destroy  a  compound  into  which  an  oxide  enters,  and 
which  prevents  the  oxide  being  reduced  by  charcoal.  The  sili- 
cate of  zinc,  for  instance,  yields  no  metallic  zinc  with  charcoal, 
unless  it  be  mixed  with  a  flux  capable  of  combining  with  the 
silica. 


IGNITION   WITH   FLUXES.  291 

"4.  To  prevent  the  formation  of  certain  alloys,  and  conse- 
quently the  combination  of  some  metals  with  others,  as  in  the 
case  of  a  mixture  of  the  oxides  of  manganese  and  iron  with  a 
suitable  flux,  the  iron  is  obtained  in  a  state  of  purity,  whereas  if 
no  flux  had  been  added,  an  alloy  would  have  been  obtained. 
Gold  and  silver  can  be  separated  from  many  other  metals  by 
means  of  a  flux. 

"  5.  To  scorify  some  of  the  metals  contained  in  the  substance 
to  be  assayed,  and  obtain  the  others  alloyed  with  a  metal  con- 
tained in  the  flux,  as  gold  or  silver  with  lead. 

"  6.  And  lastly,  a  flux  may  be  employed  to  obtain  a  single 
button  of  metal,  which  otherwise  would  be  obtained  in  globules." 

Fluxes,  as  well  as  the  substances  to  be  fluxed,  must  be  reduced 
to  the  finest  state  of  comminution  previous  to  mixture. 

When  the  mixture  is  of  a  frothing  nature,  it  is  best  to  add  it 
to  the  crucible  piecemeal,  and  to  heat  it  gradually,  so  as  to  save 
the  loss  caused  by  ejection  of  particles.  After  the  whole  has 
been  placed  in  the  crucible^  the  heat  may  be  raised  and  main- 
tained until  perfect  fusion  and  the  completion  of  the  process. 

The  mixing  of  the  charge  is  done  with  glass  rods  or  platinum 
wires,  and  the  containing  crucible  must  be  of  sufficient  capacity 
to  prevent  loss  by  the  ejection  of  particles.  The  flux  should  be 
rather  in  excess.  In  the  fluxing  of  substances  which  evolve  gases, 
the  cover  of  the  crucible  should  be  laid  on  loosely ;  but  in  those 
experiments  requiring  the  use  of  a  furnace,  the  crucible  must  be 
close  and  tight.  The  Russian  or  other  similar  lamp  will  produce 
sufficient  heat  for  ordinary  fluxions ;  and  Barren's  furnace  will 
serve  for  the  more  refractory.  When  a  platinum  crucible  is 
heated  in  a  blast  or  common  furnace,  it  should  be  imbedded  in  a 
Hessian  or  iron  crucible  lined  with  magnesia,  otherwise  it  will  be 
damaged. 

Fluxes  are  divided  into  non-metallic  and  metallic  fluxes. 

NON-METALLIC  FLUXES. — (Berthier,  Ussaispar  la  voie  Seclie.} 
— Silica  is  employed  frequently  to  cause  the  fusion  of  some 
gangues  in  assays  made  at  an  elevated  temperature.  Silica  com- 
bines with  all  the  bases,  and  forms  with  them  bodies  termed 
silicates,  which  are  more  or  less  fusible. 

Lime,  Magnesia,  and  Alumina. — It  is  known  that  no  simple 
silicate  is  readily  fusible,  so  that  lime,  magnesia,  or  alumina  are 


292  NON-METALLIC   FLUXES. 

employed,  according  to  circumstances,  to  reduce  a  simple  silicate 
to  such  a  condition  that  it  will  readily  fuse  in  an  assay  furnace. 
Sometimes,  to  attain  this  end,  it  is  requisite  to  use  all  the  above- 
mentioned  earths,  for  experience  has  proved  that,  as  a  general 
thing,  a  mixed  or  double  silicate  fuses  more  readily  and  flows 
freer  than  a  simple  silicate. 

Baryta. — Hydrate  of  baryta  fuses  at  a  low  red  heat,  and  with- 
out loss  of  its  water  of  crystallization,  and  for  the  first  reason  is 
preferable  to  either  the  carbonate  or  nitrate.  It  is  used  in  silver 
or  platinum  crucibles,  and  when  silicates  are  to  be  tested  for 
alkalies.  The  silicates  of  baryta,  however,  fuse  with  difficulty, 
and  are  sluggish. 

Glass  is  a  very  useful  flux  in  certain  iron  assays.  The  kind 
employed  must  not  contain  lead. 

Boracie  Acid. — The  native  boracic  acid,  after  fusion  and  pul- 
verization, is  to  be  employed  whenever  the  use  of  this  acid  is 
indicated.  It  ought  to  be  kept  in  well-stoppered  bottles. 

Boracic  acid  has  the  property  of  forming  with  silica  and  all 
the  bases  very  fusible  compounds,  and  is  from  this  cause  a  very 
universal  flux.  Nevertheless,  there  is  an  inconvenience  attached 
to  its  use ;  it  is  very  volatile,  so  that  sometimes  the  greater  part 
employed  in  an  assay  sublimes  before  it  has  had  time  to  perform 
its  office. 

Borax  (Biborate  of  Soda)  is  an  excellent  and  nearly  universal 
flux,  because  it  has  the  property  of  forming,  like  boracic  acid, 
fusible  compounds  with  silica  and  nearly  all  the  bases,  and  is  pre- 
ferable to  that  acid  because  it  is  much  less  volatile. 

It  may  be  used  at  a  high  or  low  temperature.  In  the  first 
case,  it  is  employed  in  the  assay  of  gold  and  silver,  because  it 
fuses  and  combines  with  most  metallic  oxides,  or  in  obtaining  a 
regulus,  that  is  to  say,  to  separate  the  metals,  their  arseniurets 
and  sulphurets,  from  any  stony  matter  with  which  they  may  be 
mixed,  because  this  salt  is  neither  oxidizing  nor  desulphurizing. 
In  the  second  place,  it  is  employed  in  the  assay  of  iron  and  tin 
ores,  as  in  the  presence  of  charcoal  it  retains  but  traces  of  their 
oxides,  and,  indeed,  much  less  than  generally  remains  with  the 
silicates. 

When  borax  is  heated  it  fuses  in  its  water  of  crystallization, 
and  undergoes  an  enormous  increase  of  volume ;  at  a  higher  tern- 


NON-METALLIC  FLUXES.  293 

perature,  it  fuses  and  forms  a  transparent  glass,  which  becomes 
dull  on  the  surface  by  exposure  to  air.  Only  the  fused  vitrified 
borax  ought  to  be  used  in  assays.  It  must  be  reduced  to  powder, 
and  kept  in  well-closed  vessels. 

Fluor  Spar  (Fluoride  of  Calcium)  is  rarely  employed  in  as- 
says, but  in  certain  cases  is  an  excellent  flux,  especially  where 
sulphates  are  present,  with  many  of  which  it  forms  very  fusible 
compounds.  The  best  proportions  are  about  equal  equivalents 
of  the  spar  and  the  anhydrous  sulphates  of  alkali,  lime,  and  oxide 
of  lead;  but  for  the  sulphate  of  baryta,  two  eqs.  of  the  spar  for 
one  eq.  of  the  sulphate. 

It  likewise  assists  in  fluxing  silicates,  partly  by  direct  union 
with  them,  and  partly  by  yielding  fluosilicic  gas,  and  leaving  lime 
to  unite  with  silica. 

Carbonate  of  Potasli  and  Carbonate  of  Soda. — It  has  been 
already  proved  that  they  possess  oxidizing  and  desulphurizing 
power ;  they  will  now  be  considered  as  fluxes. 

They  are  decomposed  in  the  dry  way  by  silica  and  the  silicates, 
with  the  separation  of  carbonic  acid.  The  presence  of  charcoal 
much  facilitates  this  decomposition. 

The  silicates  of  potassa  and  soda  fuse  readily  and  flow  freely. 

They  form  fusible  compounds  with  the  greater  part  of  the 
metallic  oxides*;  in  these  combinations  the  oxide  replaces  a  cer- 
tain quantity  of  carbonic  acid ;  but  these  compounds  are  not 
stable, — they  are  decomposed  by  carbon,  which  reduces  the  oxide, 
or  by  water,  which  dissolves  the  alkali. 

On  account  of  their  great  fusibility,  the  alkaline  carbonates 
can  retain  in  suspension,  without  losing  their  fluidity,  a  large 
proportion  of  pulverized  infusible  substances,  as  an  earth,  char- 
coal, &c. 

The  alkaline  carbonates  ought  to  be  deprived  of  their  water 
of  crystallization  for  assaying  purposes ;  in  fact,  it  would  be 
better  to  fuse  them  before  use.  They  must,  in  all  cases,  be  kept 
in  well-stoppered  vessels. 

They  may  be  used  indifferently,  but  carbonate  of  soda  is  to  be 
preferred,  as  it  does  not  deliquesce. 

A  mixture  of  both  is  far  preferable  to  either  alone,  and,  more- 
over, requires  a  lower  heat  for  its  fusion.  The  proper  propor- 
tions are  ten  parts  of  effloresced  carbonate  of  soda  and  thirteen 


294         BLACK  FLUX  AND  ITS  EQUIVALENTS. 

parts  of  dry  carbonate  of  potassa.  The  two  are  to  be  intimately 
incorporated  by  trituration,  and  the  mixture  kept  in  stoppered 
bottles.  This  flux  is  the  one  of  most  general  application. 

The  alkaline  carbonates  of  commerce  always  contain  sulphates 
and  chlorides.  In  ordinary  cases,  this  causes  no  inconvenience, 
but  there  are  circumstances  under  which  the  presence  of  sulphuric 
acid  would  be  injurious. 

Carbonate  of  potash  can  readily  be  procured  free  from  sulphate 
and  chloride  by  means  of  nitre  and  charcoal,  as  follows : — Pul- 
verize roughly  6  parts  of  pure  nitre,  and  mix  them  with  1  part  of 
charcoal ;  then  project  the  mixture  spoonful  by  spoonful  into  a 
red-hot  iron  crucible.  The  projection  of  each  spoonful  is  accom- 
panied by  a  vivid  deflagration,  and  carbonate  of  potash  is  found 
in  a  fused  state  at  the  bottom  of  the  crucible  ;  it  must  be  pul- 
verized, separated  from  excess  of  charcoal,  and  kept  in  a  dry  state 
for  use. 

Carbonate  of  soda  may  be  obtained  in  much  the  same  way,  by 
substituting  nitrate  of  soda  for  nitrate  of  potash ;  or  by  repeatedly 
crystallizing  the  carbonate  of  commerce. 

Nitrate  of  Potash. — The  presence  of  silica  or  silicates  much 
assists  its  decomposition.  It  is  used  as  an  oxidizing  agent,  the 
potash  resulting  from  its  decomposition  acting  as  flux.  To  pre- 
vent violent  action  and  ejection  of  particles  of  matter,  its  addition 
to  the  crucible  must  be  careful  and  gradual.  Nitre  is  also  em- 
ployed in  some  instances  as  a  substitute  for  nitrate  of  ammonia 
for  effecting  the  rapid  and  perfect  combustion  of  organic  sub- 
stances. 

Common  Salt  (Chloride  of  Sodium)  was  much  recommended 
by  the  older  assayers,  either  mixed  with  flux,  or  a  certain  quan- 
tity placed  above  it,  for  the  purpose  of  preserving  the  substances 
beneath  from  the  action  of  the  atmosphere,  or  to  temper  the  ac- 
tion of  such  bodies  as  cause  much  intumescence.  It  is  very  useful 
in  lead  assays.  When  it  is  used,  it  must  be  previously  pounded 
and  heated  to  dull  redness  in  a  crucible  to  prevent  its  decrepi- 
tation. 

Black  Flux  and  its  Equivalents. — Black  flux  is  both  a  reduc- 
ing and  a  fusing  agent.  It  is  a  mixture  of  carbonate  of  potash 
and  charcoal  in  a  minute  state  of  division.  It  is  much  employed, 
and  very  serviceable.  It  is  prepared  by  mixing  2  parts  of  argol 


POTASSA   SALTS.  295 

with  1  part  of  nitre,  placing  the  mixture  in  an  iron  vessel  and 
setting  it  on  fire  by  a  burning  coal  or  red-hot  rod.  When  the 
combustion  is  finished,  the  substance  is  pulverized  and  sifted 
whilst  jet  hot,  and  kept  in  well-stoppered  jars,  as  it  rapidly  ab- 
sorbs moisture  from  the  atmosphere. 

Black  flux  is  much  used  in  lead  and  copper  assays ;  but  as  it 
swells  greatly  at  the  commencement  of  the  operation,  the  cruci- 
ble must  not  be  more  than  two-thirds  full.  , 

It  can  be  readily  imagined  that,  as  it  fuses  and  reduces  at  the 
same  time,  the  relative  proportions  of  alkali,  carbonate,  and 
charcoal  ought  to  vary  according  to  the  nature  of  the  substance 
acted  upon ;  and  it  is  often  expedient  to  employ  the  greatest  pos- 
sible proportion  of  alkali  to  obtain  the  largest  yield  of  metal. 
Black  flux  may  be  obtained  richer  in  carbon  by  mixing  1  part  of 
nitre  with  2J  or  three  parts  of  argol. 

Common  black  flux  contains  5  per  cent,  of  charcoal.  The 
flux  prepared  with  2J  of  tartar  or  argol  to  1  of  nitre,  contains 
8  per  cent.,  and  that  with  3  contains  12  per  cent,  of  charcoal. 

Black  flux  can  be  replaced  by  anhydrous  or  dry  carbonate  of 
soda  mixed  with  some  reducing  •  agent.  When  charcoal  is  em- 
ployed it  must  be  reduced  to  a^very  fine  powder ;  in  fact,  it  ought 
to  be  levigated. 

The  three  following  fluxes  are  very  useful : 

.Carbonate  of  Soda,       .         .  <               .94         88         816 
Charcoal, 6         12         184 

The  second  is  very  nearly  equivalent  to  sodium  and  carbonic 
acid,  and  the  third  to  sodium  and  carbonic  oxide ;  but  it  must  be 
observed,  that  whatever  precautions  be  taken,  these  mixtures 
never  become  so  liquid  as  black  flux,  because  the  charcoal  tends 
very  much  to  separate  and  rise  to  the  surface. 

Instead  of  charcoal,  it  is  preferable  to  use  sugar  or  starch  to 
make  a  flux  equivalent  to  black  flux  with  carbonate  of  soda ;  the 
mixture  must  be  made  most  intimately. 

Cream  of  tartar,  carbonized  by  a  semi-combustion  until  it  is 
reduced  to  half  its  weight,  is  a  very  good  substitute  for  black 
flux :  it  contains  about  10  per  cent,  of  charcoal. 

Argol  (Cream  of  Tartar,  Bitartrate  of  Pot  ass  a). — When  bi- 
tartrate  of  potassa  is  heated  in  a  covered  crucible,  a  rapid  de- 
composition takes  place,  accompanied  by  a  disengagement  of  in- 


296  WHITE   OR   MOTTLED  SOAP. 

flammable  gases ;  the  substance  agglomerates,  but  without  fusing 
or  boiling  up.  The  residue  is  black,  blebby,  and  friable,  and 
contains  15  per  cent,  of  carbon  when  produced  from  rough  tartar 
or  argol,  and  7  per  cent,  from  cream  of  tartar. 

These  reagents  produce  the  same  effects  as  black  flux,  and 
possess  more  reducing  power,  because  they  contain  more  com- 
bustible matter;  but  this  is  an  inconvenience,  because  the  excess 
prevents  their  entering  into  full  fusion  when  the  substance  to  be 
assayed  requires  but  a  small  proportion  of  a  reducing  agent. 
They  can  be  used  with  success  in  assays  requiring  much  carbona- 
ceous matter. 

JSisulphate  of  Potassa  is  a  convenient  flux  for  several  mine- 
rals, such  as  for  those  highly  aluminous  (Rose),  for  chromic  and 
other  similar  ores  (Booth}. 

Salt  of  Sorrel  (Binoxalate  of  Potassa),  when  heated,  is  decom- 
posed. It  decrepitates  feebly,  and  during  its  decomposition  is 
covered  with  a  blue  flame ;  it  at  first  softens,  and  when  fully 
fused,  is  wholly  converted  into  carbonate.  When  the  oxalate  is 
very  pure,  the  resulting  carbonate  is  perfectly  white  and  free 
from  charcoal ;  but  very  often  it  is  spotted  with  blackish  marks. 
It  has  no  very  great  reducing  power. 

Cyanide  of  Potassium  acts  powerfully  both  as  a  reducing  and 
desulphurizing  reagent,  and  is  a  very  useful  flux  in  small  assays. 
According  to  Liebig  it  has  the  advantage  over  the  potassa  salts 
with  vegetable  acids,  of  not  carbonizing  the  metal,  for  the  salt 
changes  at  the  expense  of  the  metallic  oxide  into  cyanate  of 
potassa.  If  the  metallic  oxide  predominates,  the  rest  will  be  re- 
duced by  the  cyanic  acid  without  separation  of  carbon. 

White,  or  Mottled  Soap  is  a  compound  of  soda  with  a  fat  acid. 
When  heated  in  close  vessels  it  fuses,  boiling  up  considerably, 
and  during  its  decomposition  gives  off  smoke  and  combustible 
gases,  and  leaves  a  residue  composed  of  carbonate  of  soda  with 
about  5  per  cent,  of  charcoal.  Of  all  reducing  agents  soap  ab- 
sorbs the  greatest  quantity  of  oxygen,  and  as  the  residue  of  its 
decomposition  by  heat  affords  but  little  charcoal,  it  has  the  pro- 
perty of  forming  very  fluid  slags.  Nevertheless,  it  is  rarely  em- 
ployed, because  certain  inconveniences  outweigh  its  advantages. 
These  inconveniences  are,  its  bubbling  up  and  its  extreme  light- 
ness. It  also  requires  to  be  rasped,  in  order  to  mix  it  perfectly 


LITHARGE— GLASS.  297 

with  the  substances  it  is  to  decompose,  and  it  then  occupies  a 
very  large  volume,  and  requires  correspondingly  large  crucibles. 
There  are  nevertheless  cases  where  it  may  be  used  with  advantage 
by  mixing  it  with  other  fluxes. 

All  those  fluxes  containing  alkaline  and  carbonaceous  sub- 
stances are  reducing  and  desulphurizing,  besides  acting  as  fluxes, 
properly  so  called ;  they  also  produce  another  effect  which  it  is 
useful  to  know,  viz. :  they  have  the  property  of  introducing  a 
certain  quantity  of  potassium  or  sodium  into  the  reduced  metal. 
This  was  first  pointed  out  by  M.  Vauquelin.*  He  found  that 
when  oxide  of  antimony,  bismuth,  or  lead  was  fused  with  an 
excess  of  tartar,  the  resulting  metals  possessed  some  peculiar 
characters,  which  they  owed  to  the  presence  of  several  per  cent, 
of  potassium. 

METALLIC  FLUXES. — Litharge  and  Ceruse. —  These  bodies 
always  act  as  fluxes,  but  at  the  same  time  often  produce  an  alloy 
with  the  metal  contained  in  the  ore  to  be  assayed.  Ceruse  pro- 
duces the  same  fluxing  effect  as  litharge.  The  litharge  is  the 
better  flux,  and  is  very  useful  in  a  great  number  of  assays. 

It  fuses  readily  with  the  oxides  of  iron,  copper,  bismuth,  an- 
timony, and  arsenic,  sulphate  of  lead  and  the  silicates,  in  the 
proportion  of  2  to  5  parts  of  litharge  to  1  part  of  the  substance 
to  be  fluxed ;  other  oxides  require  a  larger  amount  of  litharge. 
Its  action  is  that  of  promoting  fusion,  reducing  an  oxide,  and  de- 
sulphurizing a  sulphuret. 

Glass  of  Lead  (Silicate  of  Lead}. — The  silicates  of  lead  are 
preferable  to  litharge  in  the  treatment  of  substances  containing 
no  silica,  or  which  contain  earths  or  oxides  not  capable  of  forming 
a  compound  with  the  oxide  of  lead,  excepting  by  the  aid  of  silica. 
It  may  be  made  by  fusing  1  part  of  sand  with  4  parts  of  litharge ; 
if  required  more  fusible,  a  larger  proportion  of  litharge  must  be 
added. 

Borates  of  Lead. — The  borates  of  lead  are  better  fluxes  than 
the  silicates  when  the  substance  to  be  assayed  contains  free 
earths ;  but  in  order  to  prevent  them  swelling  up  much  when 
fused,  they  must  contain  an  excess  of  oxide  of  lead.  The  borate 
of  lead  containing  *9056  of  oxide  of  lead,  and  *0944  of  boracic 

*  Annales  des  Mines. 


298  CALCINATION. 

acid,  is  very  good.     Instead  of  borate  of  lead,  a  mixture  of  fused 
borax  and  litharge  may  be  employed ;  it  is  equally  serviceable. 

Sulphate  of  Lead  is  decomposed  by  all  silicious  matters  and 
by  lime,  so  that  when  these  substances  are  present  litharge  is 
produced,  which  fluxes  them. 

Oxide  of  Copper  is  rarely  used  as  a  flux  for  oxidated  matters, 
but  is  sometimes  employed  in  the  assays  of  gold  and  zinc  to  form 
an  alloy  with  those  metals.  In  this  case  a  reducing  flux  must  be 
mixed  with  the  oxide.  Metallic  copper  may  be  used,  but  is  not 
so  useful,  as  it  cannot  be  so  intimately  mixed  with  the  assay. 

Oxides  of  Iron  are  good  fluxes  for  the  silicates.  They  are, 
however,  rarely  employed  for  that  purpose  ;  they  are  more  often 
used  to  introduce  metallic  iron  into  an  alloy  to  collect  an  infusible 
or  nearly  infusible  metal,  by  alloying  it  with  iron,  such  as  man- 
ganese, tungsten,  or  molybdenum. 

CALCINATION. — The  separation  (in  a  dry  way)  of  volatile  from 
fixed  matter,  by  heat,  is  termed  calcination.  The  process  is  ap- 
plicable 

To  the  expulsion  of  water  from  salts,  minerals,  coals,  and  other 
substances. 

"  "  carbonic  acid  from  certain  carbonates. 

"  "  arsenic  and  sulphur  from  cobalt,  nickel,  and 

other  sulphuretted  compounds. 

"  "  bituminous  matter  from  coals,  and  certain 

minerals  and  ores. 
To  the  ignition  of  quartz  and  silicious  minerals  to  promote  their 

disintegration. 
For  the  purpose  of  expelling  the  combined  water  of  argillaceous 

minerals,  and  of  thus  rendering  them  more  obstinate  to  the 

solvent  action  of  acids  and  reagents. 

If  the  substance  under  process  is  organic,  its  calcination  in  a 
close  vessel  by  a  medium  heat  usually  effects  only  partial  decom- 
position, the  gaseous  matter  generated  escaping  through  inter- 
stices, and  the  fixed  components  remaining  with  a  portion  of  un- 
altered carbon.  Performed  in  this  manner,  the  process  takes  the 
name  of  coking,  familiar  instances  of  which  are  the  formation  of 
coke  by  distilling  coal  in  closed  retorts,  the  manufacture  of  char- 
coal from  wood,  and  of  bone  black  from  bones. 

By  increasing  the  temperature  and  admitting  the  air,  the  whole 


BOASTING.  299 

of  the  alterable  and  volatile  matter  is  expelled,  the  fixed  matter 
remaining  as  ashes.  The  process  is  then  styled  incineration, 
and  in  this  way  the  coke,  charcoal,  and  ivory  black,  obtained  as 
above  directed,  may  be  entirely  reduced  to  their  incombustible 
portions  or  ashes. 

Calcination  is  effected  in  platinum  spoons  or  crucibles,  in  deli- 
cate experiments,  over  a  spirit-lamp ;  but  in  large  operations  a 
furnace  is  required,  and  the  containing  vessels  are  crucibles,  of 
either  metal  or  earthenware,  according  to  the  nature  of  the  sub- 
stance to  be  heated,  though  the  latter  are  often  unsuitable  for 
temperatures  above  a  red  heat. 

When  the  operation  is  finished,  the  crucible  should  be  taken 
from  the  fire  and  allowed  to  cool  gradually.  The  cover  is  then 
to  be  lifted  off,  and  the  contents  taken  out  with  a  spatula,  and 
the  portions  adhering  to  the  sides  removed  with  a  feather. 

If  the  substance  undergoing  calcination  is  fusible,  it  is  neces- 
sary, when  quantities  are  to  be  ascertained,  to  weigh  both  the 
crucible  and  contents  before  ignition,  so  that  the  amount  of  vola- 
tile matter  driven  off  may  be  expressed  by  thevweight  lost  in 
heating.  Water  alone,  or  acidulated,  with  the  aid  of  heat,  gene- 
rally removes  the  calcined  matter  from  the  crucible. 

A  body  decrepitating  by  heat  should  be  powdered  before  being 
subjected  to  the  process  of  calcination,  and  the  temperature 
should  be  raised  slowly  and  gradually,  otherwise  when  the  cru- 
cible is  not  covered,  a  loss  [may  result  from  the  ejection  of 
particles. 

To  avoid  contact  with  the  generated  vapors  or  with  the  atmo- 
sphere, which  to  some  substances  act  as  reducing  agents,  the 
crucible  should  in  such  cases  be  covered,  and,  if  tightly  luted,  per- 
forated with  one  or  more  small  holes  for  the  escape  of  vapor. 

ROASTING. — This  process,  as  generally  understood,  is  a  kind  of 
calcination  to  which  many  ores  are  submitted  before  their  final 
reduction  to  the  metallic  state,  for  the  purpose  of  expelling  ingre- 
dients which  would  either  delay  that  process  or  be  injurious  to 
the  metal  when  extracted.  In  this  way,  water,  carbonic  acid, 
sulphur,  selenium,  arsenic,  and  sometimes  other  substances,  are 
driven  off  from  the  ores  containing  them.  The  term  is  also  ap- 
plied to  other  processes,  among  the  most  important  of  which  is 
that  of  the  exposure  to  heat  and  air,  by  which  metals  become 


300  DEFLAGRATION. 

altered  in  composition.  Thus,  copper  becomes  oxidized,  and 
antimony  and  arsenic  acidified  by  union  with  oxygen. 

Roasting  is  always  effected  in  broad,  shallow  open  vessels,  so 
that  the  air  may  have  free  access ;  and  in  order  to  promote  the 
absorption  of  oxygen  or  the  escape  of  the  volatile  substance,  the 
surface  of  the  body  to  be  heated  should  be  increased  by  previous 
pulverization,  and  it  should  be  constantly  stirred  during  the  ope- 
ration, so  as  to  present  as  many  points  of  contact  as  possible. 
The  most  suitable  vessel  is  a  baked  earthenware  saucer  or  cap- 
sule placed  in  a  muffle  or  upon  the  bars  of  a  calcining  furnace. 
Sometimes  a  crucible  is  used,  and  then  the  position  of  the  vessel 
in  the  furnace  should  be  slightly  inclined  on  one  side.  In  either 
case  the  vessels  should  be  heated  to  dull  redness  previous  to 
receiving  their  charge. 

That  species  of  roasting  termed  deflagration  is  effected  by 
rapidly  heating  the  substance  to  be  oxidized,  together  with  some 
additional  body  as  an  oxidizing  agent,  as  a  nitrate  or  chlorate, 
for  instance.  The  powdered  mixture  is  added  portionwise  to  the 
crucible  previously  heated,  and  maintained  at  redness  during  the 
operation.  The  vivid  and  sudden  combustion  which  ensues  modi- 
fies the  composition  of  the  original  substance,  and  increases  its 
amount  of  oxygen  at  the  expense  of  the  addendum.  Thus,  for 
instance,  sulphuret  of  arsenic  is  deflagrated  with  nitre,  to  produce 
arseniate  of  potassa,  titanium;  and  certain  other  metals  to  be 
transformed  into  oxides. 

Deflagration  is  also  used  as  a  means  of  detecting  the  presence 
of  nitric  or  chloric  acids.  For  this  purpose  the  suspected  sub- 
stance is  to  be  heated  with  cyanide  of  potassium,  in  a  small  pla- 
tinum spoon.  If  deflagration  ensues,  it  is  a  test  of  the  presence 
of  one  of  them,  or  a  compound  of  one  of  them. 

The  crucibles  may  be  of  clay  or  metal,  according  to  the  nature 
of  the  substance  to  be  heated.  The  roasting  of  substances  for 
the  expulsion  of  organic  matter  may  be  effected  in  platinum  ves- 
sels, provided  the  heat  is  not  carried  sufficiently  high  to  produce 
fusion  of  the  substance  being  roasted. 

The  heat  must,  at  first,  be  very  gradually  applied,  and  at  no 
time  be  made  great  enough  to  fuse  or  agglutinate  the  material, 
otherwise  the  process  will  have  to  be  suspended  in  order  to  re- 
pulverize  the  matter.  Proper  care  at  the  commencement  will 


REDUCTION.  301 

obviate  the  necessity  of  this  additional  trouble.  When  the  heat 
has  been  cautiously  raised  to  redness  and  all  liability  of  fusion  is 
over,  the  fire  may  be  urged  to  the  production  of  a  yellowish  red 
or  even  white  heat,  so  that  the  expulsion  of  volatile  matter  may 
be  complete. 

Roasting  operations  which  disengage  deleterious  or  disagree- 
able fumes  should  be  carried  on  in  the  open  air  or  under  a  hood, 
and  when  the  volatile  matters  are  valuable,  they  may  be  condensed 
as  directed  in  DISTILLATION  and  SUBLIMATION. 

Decrepitation,  which  frequently  occurs  and  occasions  loss  by 
ejection  of  particles  of  the  mixture,  is  owing  to  the  sudden  va- 
porization of  the  water  of  crystallization,  or  water  mechanically 
confined,  which  in  finding  vent  scatters  the  confining  substance 
with  a  crackling  noise.  To  prevent  this  loss,  the  crucible  should 
be  loosely  covered  until  decrepitation  ceases. 

REDUCTION. — This  operation  illustrates  the  use  of  tubes  in  ex- 
periments requiring  the  application  of  high  heat.  It  is  employed 
for  the  separation  of  metallic  bases  from  any  bodies  with  which 
they  are  combined ;  but  is  generally  confined  to  the  extraction 
from  an  oxide — that  being  the  kind  of  combination  most  com- 
monly met  with.  The  combined  action  of  heat  and  certain  re- 
agents is  required  to  effect  this  result,  the  temperature  varying 
with  the  nature  of  the  substance  to  be  reduced.  ,  - 

The  most  usual  reducing  agents  are  charcoal  and  hydrogen 
gas.  Tallow,  oil,  and  resin  are  sometimes  used,  but  being  easily 
decomposed  they  are  dissipated  before  entire  reduction  has  oc- 
curred. Sugar  and  starch  are  also  occasionally  employed. 
We  shall,  however,  confine  our  remarks  to  the  two  principal 
articles. 

Reduction  ly  Charcoal. — Charcoal  is  used  for  this  purpose  in 
two  ways,  either  in  powder  and  directly  mixed  with  the  substance, 
or  as  a  lining  coat  to  the  crucible  in  which  the  reduction  is  ac- 
complished. The  first  mode  is  objectionable,  because  the  excess 
of  coal  which  is  required  to  be  used  interferes  with  the  agglomera- 
tion of  the  particles  of  reduced  metal.  Whenever  it  is  adopted, 
the  quantity  of  coal-dust  to  be  added,  which  must  be  sufficient  to 
transform  all  the  oxygen  of  the  oxide  into  carbonic  acid,  can  be 
determined  by  calculation.  This  amount  is  then  mixed  thoroughly 
with  the  Oxide  previously  powdered,  and  is  transferred  to  a  cru- 


302  REDUCTION. 

cible,  taking  care  to  place  the  charge  in  the  centre,  and  to  cover 
the  contents  with  a  layer  of  the  dust.  The  whole  is  then  to  be 
subjected  to  the  heat  of  a  furnace,  assisted  if  necessary,  by  a  blast, 
The  reduction  in  this  way,  the  most  convenient  for  large  quan- 
tities, is  rapid  and  complete,  but  the  metallic  residue  is  often 
mixed  with  coal-dust. 

In  general,  the  mere  contact  of  carbon  is  sufficient  to  effect  re- 
duction, and  consequently  the  inconvenience  of  the  above  plan 
may  be  avoided  by  the  use  of  a  brasque  or  crucible  lined  inte- 
riorly with  charcoal.  An  earthen  crucible  is  very  readily 
brasqued  as  follows : — A  mixture  of  three  parts  of  charcoal-dust, 
and  two  parts  of  powdered  clay,  is  mixed  with  water  and  kneaded 
into  a  plastic  dough.  The  bottom  of  the  crucible  is  then  covered 
with  this  dough,  and  a  wooden  cylindrical  core  of  diameter  equal 
to  that  required  for  the  cavity,  is  inserted  in  the  centre  and  sur- 
rounded with  more  of  the  same  dough,  which  is  compressed  with 
the  fingers  at  each  addition  so  as  to  make  the  whole  as  compact 
as  possible.  The  core  is  then  to  be  carefully  withdrawn,  and  the 
crucible  placed  aside  to  dry.  A  platinum  crucible,  which  is  as 
applicable  as  clay  for  certain  operations,  can  be  brasqued  in  the 
same  way.  Some  operators  use  the  coal-dust  without  clay,  and 
moisten  it  with  water  or  oil.  The  crucibles  should  be  free  from 
external  fissures  to  prevent  access  of  air,  and  must  always  be 
covered  when  heated.  The  reduction  by  this  plan  is  slower  than 
by  the  first  mode,  and  requires  a  higher  temperature,  but  the 
metal  as  procured  is  cleaner. 

The  powdered  oxide  is  placed  in  the  cavity  in  sufficient  quan- 
tity to  fill  it,  then  compressed  with  the  fingers  and  covered  with 
a  layer  of  coal-dust.  The  cover  being  luted  upon  the  crucible 
the  whole  is  to  be  heated  in  a  blast  furnace.  The  reduction  pro-, 
ceeds  from  the  surface,  that  part  of  the  oxide  next  to  the  char- 
coal being  first  acted  upon.  The  time  required  depends  upon 
the  nature  of  the  oxide,  the  degree  of  temperature,  and  the 
quantity  under  process  ;  sometimes,  particularly  when  the  metals 
are  very  fusible,  the  reduced  particles  collect  in  a  clean  lump  at 
the  bottom  of  the  crucible,  and  are  easily  removable  when  cold, 
with  the  finger  or  spatula.  Others  again,  more  refractory,  form 
a  very  friable  lump  of  metallic  powder. 

Reduction  ly  Hydrogen. — This  mode,  which  is  much  used  in 


REDUCTION  APPARATUS. 


303 


analyses,  consists  in  passing  a  current  of  hydrogen  gas  over  the 
metallic  oxides  heated  to  redness  in  a  glass,  or  better,  porcelain 
tube,  and  is  equally  applicable  to  some  chlorides  and  other  com- 
pounds. The  arrangement  of  the  requisite  apparatus  is  shown 
in  Fig.  218.  A  is  a  flask  for  the  disengagement  of  hydrogen 

Fig.  218. 


gas,  by  the  action  of  dilute  sulphuric  acid  upon  zinc,  the  fun- 
nelled tube  a  being  for  the  ingress  of  the  acid.  The  disengage- 
ment tube  b  is  bent  at  right  angles  and  bulbed  midway  in  its 
horizontal  arm.  The  bulb  is  to  be  furnished  with  a  plug  of  raw 
cotton  for  the  condensation  and  retention  of  any  aqueous  vapor 
that  may  pass  over.  This  tube  is  joined  hermetically  to  another 
short  tube  c  by  means  of  an  india-rubber  connection.*  The 

*  The  use  of  india-rubber  as  a  material  for  forming  flexible  joints  is  one  of  the 
most  important  aids  in  chemical  manipulation.  Its  property  of  readily  uniting  at 
freshly  cut  surfaces,  its  flexibility,  its  ready  and  close  adhesion  to  surfaces,  and 
power  of  resisting  the  action  of  corrosive  vapors,  except  those  of  chlorine,  sulphuric 
and  nitric  acids,  and  a  few  others,  render  it  peculiarly  excellent  for  many  mechani- 
cal purposes  of  the  laboratory.  Tubes  of  any  shape  and  size,  according  to  the 
form  and  dimensions  of  the  parts  of  apparatus  to  be  connected,  are  to  be  fashioned 
out  of  it  with  almost  equal  facility.  For  the  transmission  of  corrosive  vapors  or 
gases  they  should  have  an  outer  layer,  the  seam  in  which  must  be  directly  oppo- 
site to  that  in  the  tube  which  it  invests,  so  as  to  insure  perfect  tightness.  Prof. 
Booth  uses  the  india-rubber  pipe,  made  by  Goodyear,  as  conduits  for  steam  in  boil- 
ing corrosive  liquids  by  that  agent,  and  gives  it  consistence  with  flexible  lead  pipe, 
which  he  covers  externally  and  internally.  A  better  framework  would  be  a  spiral 


30i  GAS-BAGS. 

connecting  tube  is  made  of  sheet  caoutchouc,  about  one-twelfth  of 

an  inch  in   thickness.     A  piece  of 
Flg-219>  the  required  length  of  the  tube  and 

twice  the  intended  width  is  cut  out 
and  wrapped  around  a  cylindrical 
glass  rod  d,  Fig.  219,  of  diameter 
very  nearly  as  great  as  that  for  the 
tube  to  be  formed.  The  ends  are 
then  brought  closely  together  by 
compression  between  the  thumb  and 

fingers  as  at  &,  and  the  excess  removed,  close  to  the  surface  of 
the  rod,  with  a  pair  of  clean  sharp  scissors.  The  freshly  cut 
edges  being  further  pinched  together  throughout  the  length  of 
the  tube,  form  a  close,  air-tight,  scarcely  perceptible  joint.  The 
rod  is  then  to  be  withdrawn,  and  the  tube  thus  formed  carefully 
drawn  over  the  end  of  one  of  the  glass  tubes  to  be  connected,  so 
as  to  form  an  extension  for  the  reception  of  the  end  of  the  other. 
The  two  ends  should  approach  each  other  almost  to  contact,  a 
minute  interval  being  necessary  to  afford  the  requisite  flexibility. 
This  junction-pipe  is  fastened  to  the  surface  of  the  tube  by  fine 
twine  wrapped  or  tied  around  each  of  its  ends,  as  shown  at  rr? 
Fig.  218. 

The  gas-bottle  thus  fitted  is  connected,  by  means  of  a  per- 

coil  of  wire.  The  tubing  made  of  canvas  imbued  with  caoutchouc  is  less  durable, 
and  does  not  admit  of  such  general  application. 

Before  forming  the  tube  above  mentioned,  it  is  better  to  warm  the  caoutchouc, 
by  which  its  flexibility  is  increased  and  its  cut  surface  made  to  adhere  more 
readily  and  closely.  The  scissors  cut  more  freely  when  previously  moistened. 
These  flexible  joints  not  only  relieve  the  apparatus  of  stiffness  and  consequent 
liability  to  fracture,  but  enable  the  operator  to  adjust  it  more  rapidly  and  satisfac- 
torily than  he  could  possibly  do  without  them.  A  little  practice  upon  shreds  will 
give  great  proficiency  in  the  art  of  forming  india-rubber  tubes  arid  joints. 

India-rubber  for  this  purpose  is  now  made  by  Goodyear,  New  York,  who  sells 
it  in  sheets  of  various  sizes.  Ready-made  tubing  of  various  bores  is  also  furnished 
by  the  same  manufacturer.  Gas  bags  are  likewise  made  of  caoutchouc.  The 
larger  sizes,  pp.  170,  172,  are  to  be  procured  from  the  manufacturer.  Smaller 
ones,  for  nice  purposes,  may  be  readily  made  from  the  rubber  bottles  of  the  shops. 
One  of  uniform  thickness,  and  as  free  as  possible  from  indentations  and  imper- 
fections, is  softened  in  boiling  water  or  by  exposure  for  several  days  to  contact 
with  ether,  and  then  adjusted  upon  a  stop-cock  with  a  syringe  attached.  The  air 
must  next  be  injected  slowly,  so  that  the  expansion  of  the  bag  may  be  gradual  and 
uniform  throughout  all  its  parts ;  or  the  bag  may  very  conveniently  be  blown  out 
with  the  mouth. 


REDUCTION    BY    HYDROGEN. 


305 


forated  cork  with  the  drying-tube  d,  filled  with  lumps  of  dried 
chloride  of  calcium.  At  the  opposite  end  of  the  drying-tube  e, 
is  another  tube  with  a  bulb  blown  in  its  centre,  for  the  reception 
of  the  substance  to  be  reduced,  and  in  which  it  is  heated  by  the 
flame  of  a  spirit-lamp.  This  tube,  like  the  other,  is  annexed  by 
elastic  joints  to  the  short  tube  connected  with  the  desiccating- 
tube  through  a  perforated  cork. 

This  plan,  first  proposed  by  Berzelius,  was  used  by  him  in  the 
synthesis  of  water,  binoxide  of  copper  being  the  substance  em- 
ployed to  abstract  the  hydrogen,  its  oxygen  forming  water  there- 
with. 

A  modification  of  the  foregoing  apparatus  is  shown  by  Fig.  220, 


which  exhibits  a  closed  crucible  of  platinum,  as  the  receiver,  in 
place  of  a  glass  bulb,  it  being  necessary,  in  certain  instances,  to 
exclude  the  direct  contact  of  air  during  and  immediately  after 
the  heating. 

Hydrogen  is  a  powerful  reducing  agent,  and  leaves  the  metal 
absolutely  pure.  At  a  red  or  white  heat,  its  action  will  reduce 
the  oxides  of  lead,  bismuth,  copper,  antimony,  zinc,  iron,  cobalt, 
nickel,  tungsten,  molybdenum,  and  uranium. 

The  heat  should  not  be  applied  to  the  bulb  until  it  is  entirely 
freed  from  air,  which  may  be  done  by  allowing  the  hydrogen  to 
pass  over  some  minutes  previously.  A  disregard  of  this  precau- 
tion may  cause  an  explosion  from  the  combustion  of  a  mixture  of 
hydrogen  and  atmospheric  air. 

The  above  apparatus  answers  very  well  for  decomposing  me- 
tallic sulphurets  by  chlorine.  It  is  also  applicable  for  heating 
solids  in  gases,  and  serves  for  the  preparation  of  chloride  of  sul- 

20 


306  REDUCTION  BY  CARBONIC  OXIDE. 

phur,  of  phosphorus,  and  of  many  other  volatile  chlorides.  For 
this  purpose  it  is  only  necessary  to  replace  the  flask  A  by  other 
suitable  generating  vessels,  and  the  extreme  end  of  the  exit  tube 
by  a  tubulated  retort  with  its  beak  bent  downwards  and  leading 
into  the  recipient,  kept  cool  by  a  frigorific  mixture. 

The  tubes  for  these  purposes  must  be  of  hard  glass  and  entirely 
free  from  lead,  and  not  exceeding  a  third  of  an  inch  in  width. 
The  bulbs  should  be  of  1 J  inch  diameter.  The  chlorcalcium  tube 
may  be  three-fourths  of  an  inch  wide.  >,, 

There  are  other  modes  of  reduction,  of  less  general  application, 
however,  than  the  preceding.  Metals  may  be  precipitated  in  a 
free  state,  in  some  instances,  from  solutions,  by  presenting  bodies 
for  which  their  oxygen  has  a  stronger  affinity ;  thus,  for  example, 
protosulphate  of  iron  precipitates  metallic  gold;  phosphorous 
acid,  mercury  ;  and  formic  acid  or  formate  of  soda,  both  of  these 
metals,  and  also  silver  and  platinum,  if  the  liquids  containing 
them  in  solution  are  boiled.  So  also  one  metal  may  reduce 
another  if  the  affinity  of  the  first  for  oxygen  is  greater  than  that 
of  the  last.  Thus  metallic  copper  throws  down  mercury,  silver, 
and  arsenic,  from  their  solutions,  and  iron  precipitates  copper. 

Metals  are  also  reduced  by  galvanic  action,  practical  illustra- 
tions of  which  are  seen  in  the  galvanoplastic  art.  All  oxides 
which  resist  the  combined  action  of  heat  and  charcoal  or  hydrogen, 
are  reduced  by  the  agency  of  galvanism. 

Reduction  by  Carbonic  Oxide. — Another  convenient  agent  of 
reduction,  employed  in  the  same  manner  as  hydrogen,  is  carbonic 
oxide,  made  on  a  small  scale  by  the  action  of  oil  of  vitriol  on 
oxalic  acid,  and  separation  of  the  carbonic  acid  produced  at  the 
same  time,  by  milk  of  lime.  It  readily  reduces  the  metallic 
oxides  of  nickel,  iron,  zinc,  that  of  lead  at  a  very  low  tempera- 
ture, and  that  of  copper  below  a  red  heat.  For  heating  in  manu- 
facturing processes,  it  is  made  by  regulating  the  admission  of  air 
to  a  deep  bed  of  ignited  anthracite  or  other  coals,  and  driving  a 
blast  of  air  horizontally  through  the  gas  as  it  issues  from  the  ,fire, 
all  other  access  of  air  being  prevented.  It  has  in  this  manner 
been  applied  to  reheating  and  puddling  furnaces.  Carbonic 
oxide  is  doubtless  the  great  reducing  agent  in  large  metallurgic 
operations. 

Roasting  and  Reduction  in  Tubes. — In  very  delicate  experi- 


ROASTING   AND    REDUCTION   IX   TUBES. 


307 


ments,  and  particularly  when  the  volatile  matter  expelled  by  the 
heat  is  to  be  collected  for  examination,  roasting  and  reduction 
are  effected  in  small  glass  tubes  closed  at  one  end.  The  glass 
must  be  white,  difficultly  fusible,  and  free  from  lead.  The  sub- 
stance is  placed  in  the  lower  or  closed  end  of  the  tube,  which  is 
then  inclined  and  heated  over  the  spirit-lamp,  as  shown  in  Fig. 
229.  In  this  way  sulphur  and  arsenic  may  be  sublimed  from 
certain  of  their  compounds,  and  mercury  from  less  volatile  metals. 
By  leaving  the  tube  open  at  both  ends  so  as  to  allow  free  access 
of  air,  many  volatile  bodies  are  oxidized,  and  collect,  on  congela- 
tion, in  the  upper  part  of  the  vessel.  Those  tubes,  with  a  bulb 
blown  at  their  lower  end,  as  shown  at  1,  5,  in  Fig.  221,  are  most 
applicable  for  decrepitating  substances. 

Fig.  221. 


J  4 

^}  5 


The  above  drawing  exhibits  the  several  forms  of  tubes  used  for 
the  reduction  of  metals,  and  particularly  the  separation  of  ar- 
senic and  mercury  from  more  fixed  matter.  Any  of  these  forms, 
or  even  a  small  test-tube  4,  will  answer.  Berzelius  prefers  the 
shape  of  1 ;  Rose  that  of  2 ;  Liebig  that  of  3 ;  and  Clarke  that 
of  5. 

The  letters  a  b  c  in  2,  and  b  in  3,  indicate  the  position  of  the 
substance  to  be  roasted  together  with  its  reducing  agent,  and  d 
and  a  in  2  and  3,  the  rings  of  condensed  volatile  matter  sub- 
limed by  the  heat.  Berzelius  and  Rose's,  and  Liebig's  tubes  are 
three  inches  in  length ;  Clarke's  two  inches.  Their  diameters  vary 


308 


PORCELAIN    AND    METALLIC    TUBES. 


from   one-sixteenth  to  one-fourth  of  an  inch,  according  to  the 
amount  of  substance  to  be  heated. 

Combustion  in  Grlass  Tubes. — The  tube  which  contains  the 
substance  to  be  heated,  should  be  made  of  hard  and  refractory 
glass  entirely  free  from  lead.  Its  position  in  the  furnace  is 
shown  by  Fig.  139,  which  has  already  been  fully  explained. 
When  it  is  designed  to  apply  a  very  intense  heat  to  the  tube,  the 
latter  should  be  enveloped  in  a  jacket,  to  prevent  its  bursting  or 
blowing  out  in  places.  This  jacket  is  a  strong  iron  plate  mould, 
with  a  lining  of  plaster  of  Paris.  It  is  shown  in  two  half  por- 
tions, as  well  as  closed,  by  the  annexed  figure. 

Fig.  222. 


The  two  semi-cylinders  are  bound  into  one  by  iron  wedge  fas- 
tenings ;  and  throughout  the  circumference  it  is  perforated  with 
holes.  Plaster  of  Paris  having  been  made  into  stiff  paste,  with 
a  little  water  and  cow's  hair,  each  half  of  the  mould  is  then  filled 
with  it ;  the  combustion-tube  next  imbedded  in  one  of  them,  and 
when  the  plaster  begins  to  set,  the  other  is  placed  on  top,  and 
the  two  fastened  together.  When  the  plaster  has  hardened,  it  is 
ready  to  be  heated ;  but  the  heat  must  be  gradual  at  the  early 
part  of  the  operation. 

Porcelain  and  Metallic  Tubes. — For  the  reduction  of  some 
oxides  by  contact  with  gases  at  furnace  temperature,  for  the 
decomposition  of  certain  organic  matters,  such  as  oils,  &c.,  and 
for  effecting  many  combinations  of  gases  with  solids,  the  glass 
tubes  are  replaced  by  those  of  porcelain,  iron,  or  platinum. 

Porcelain  tubing  should  be  selected  with  care.     It  should  be 


PORCELAIN   AND    METALLIC    TUBES.  309 

straight,  perfectly  cylindrical,  free  from  defects,  glazed  inter- 
nally, and  as  thin  as  possible.  These  tubes  are  adjusted  in  man- 
ner as  directed  for  those  of  glass,  and  heated  over  the  furnace, 
Fig.  126 ;  but  as  they  are  not  refractory,  care  must  be  taken  in 
heating  them.  It  is  advisable  to  give  them  an  exterior  coating 
of  fire  lute,  and  then  dry  them.  The  fire  should  be  ignited,  and 
all  moisture  expelled  from  the  charcoal  before  they  are  placed  in 
the  furnace,  otherwise  their  fracture  may  result.  It  is  indispen- 
sable, too,  that  the  heat  shall  be  carefully  managed,  and  after 
the  completion  of  the  process,  the  tube  must  not  be  removed 
from  the  furnace  until  it  has  entirely  but  gradually  cooled. 

Iron  tubes  are  used  for  the  decomposition  of  water,  potassa, 
and  for  other  operations  to  which  those  of  glass  and  porcelain  are 
not  adapted,  by  reason  of  inability  to  withstand  high  heat.  Gas 
tubing  is  the  most  economical,  and  can  be  had  of  all  lengths  and 
diameters.  These  also  should  be  covered  exteriorly  with  luting 
so  as  to  prevent  the  oxidation  of  the  iron  by  the  fire. 

Metallic  tubes  of  small  size  may  be  heated  over  the  furnaces, 
Fig.  139,  but  those  of  larger  dimensions  require  the  use  of  the 
furnace,  Fig.  126.  The  circular  openings  x,  x,  in  each  side,  are 
especially  for  the  passage  of  a  tube.  The  grate  should  be  ele- 
vated, so  that  the  fire  may  entirely  surround  it. 

Metallic  tubes  are  adjusted  to  generating  and  other  apparatus 
by  means  of  metallic  couplings,  gallows  screws,  or,  in  some  cases, 
by  fire  lute.  This  latter  does  not  make  a  secure  or  tight  joint, 
and  is  only  used  in  the  absence  of  more  convenient  means.  The 
ends  of  the  tube  should  project  far  enough  beyond  the  sides  of 
the  furnace  to  allow  their  refrigeration  when  necessary.  The 
gas  may  be  introduced  directly  from  the  generating  vessel,  or 
from  a  caoutchouc  bag  or  gasometer,  merely  by  adjusting  the 
end  of  the  tube  with  the  mouth  or  outlet  by  a  suitable  coupling. 
The  resultant  product  may,  in  like  manner,  be  collected  by  simi- 
lar adaptations  to  the  other  end. 

Fragments  of  flint  or  coils  of  iron  or  of  platinum  wire,  placed 
within  the  tube,  increase  the  points  of  contact  of  the  contained 
matter  and  greatly  promote  its  heating. 

As  short  tubes  are  occasionally  used  for  effecting  the  combina- 
tion of  substances  alterable  by  exposure  in  a  hot  state,  they 


310  CUPELLATION. 

should,  for  such  purposes,  be  fitted  at  the  ends  with  screw  plugs, 
to  prevent  access  of  air. 

Platinum  tubes  are  only  used  on  rare  occasions  for  particular 
.purposes,  to  which  those  of  glass,  porcelain,  or  iron,  are  inap- 
plicable, ^v^- 


^'V  J&   '•''/'.  '  •'  M"? 

CHAPTER    XVI. 

CUPELLATION. 

GOLD  and  silver  are  assayed  by  the  agency  of  heat  and  litharge 
in  shallow,  slightly  conical   crucibles,  Fig.  223,  called  cupels. 


Fig.  223. 
_M Bf  « 


a. SL H. 


This  process  separates  these  metals  from  any  debasing  admixture; 
for,  when  the  alloy  is  heated  together  with  litharge,  all  but  the 
precious  metals  are  oxidized ;  and  the  oxides  thus  formed,  to- 
gether with  the  semi-vitreous  litharge,  are  absorbed  by  the  cupel, 
whilst  the  nobler  metal  remains  as  a  button  of  absolute  purity. 

Cupels. — These  small  crucibles  are  generally  made  of  bone- 
ash,  because  that  material  fulfils  better  than  any  other  the  neces- 
sary requirements.  It  is  resistant  to  the  action  of  the  fused 
oxides  of  lead  and  bismuth,  and  by  its  porosity  facilitates  the 
penetration  of  the  oxides,  and  at  the  same  time  is,  when  made 
into  shape,  strong  enough  to  bear  handling  without  fracture. 
The  cupels  used  at  the  United  States  Mint  are  made  in  a  matrix 
of  If  inches  diameter.  The  semicircular  cavity  is  two-fifths  of  an 
inch  deep  in  the  centre.  This  size,  however,  can  be  varied  and 
they  may  be  made  smaller  or  larger  according  to  the  quantity  of 
matter  to  be  operated  upon.  Their  mode  of  manufacture  is  as 
follows : — Take  bones  or  bone-black  and  calcine  them  in  an  open 
crucible  until  the  expulsion  of  all  animal  and  carbonaceous 
matter,  which  is  known  by  the  residue  assuming  a  whitish  ap- 
pearance. Empty  the  cooled  contents  of  the  crucible  into  clean 
water,  and  give  it  repeated  washings  in  fresh  waters  to  remove 
all  soluble  matter;  filter  and  dry.  The  dried  matter  is  pure 


CUPELS.  311 

phosphate  of  lime  with  a  minute  portion  of  partially  decomposed 
carbonate. 

Make  the  powder,  calcined  and  purified  as  directed  above,  into 
a  paste  with  water  or  preferably  with  beer  (Mitchell),  in  the  pro- 
portion of  4  Ibs.  of  bone  ash  to  half  a  pound  of  beer.  The  above 
mixture  is  just  sufficiently  moist  to  adhere  strongly  when  well 
pressed,  but  not  so  moist  as  to  adhere  to  the  finger  or  the  mould 
employed  to  fashion  the  cupels.  The  mould,  Fig.  224,  of  polished 
iron  consists  of  two  pieces,  one  a  ring  having  a  conical  opening ; 
the  other,  a  pestle  having  a  hemispherical  end  fitting 
the  larger  opening  of  the  ring.  In  order  to  mould 
the  cupels,  proceed  as  follows :  Fill  the  ring  with 
the  composition,  then  place  the  pestle  upon  it,  and 
press  down  as  much  as  possible.  By  this  means, 
the  moistened  bone-ash  will  become  hardened,  and 
take  the  form  of  the  pestle ;  and  the  latter  must  then 
be  struck  on  the  head  with  a  heavy  mallet,  to  insure 
greater  consolidation  of  the  cupel.  It  is  then  to  be  turned  lightly 
round,  so  as  to  smooth  the  inner  surface  of  the  cupel,  and  with- 
drawn ;  after  which  the  cupel  must  be  removed  from  the  mould 
by  a  gentle  pressure  on  the  narrowest  end.  When  in  this  state, 
the  cupel  must  be  dried  gently  by  a  stove  \  and  lastly,  heated  in 
a  muffle,  to  expel  all  moisture.  It  is  then  ready  for  use. 

There  are  two  or  three  points  to  be  observed  in  manufacturing 
the  best  cupels.  Firstly,  the  powdered  bone-ash  must  be  of  a 
certain  degree  of  fineness ;  secondly,  the  paste  must  be  neither 
too  soft  nor  too  dry  ;  and  thirdly,  the  pressure  must  be  made 
with  a  certain  degree  of  force.  A  coarse  powder,  only  slightly 
moistened  and  compressed,  furnishes  cupels  which  are  very 
porous,  and  break  on  the  least  pressure,  and  which  allow  small 
globules  of  metal  to  enter  into  their  pores, — the  most  serious  in- 
convenience of  all. 

When,  on  the  contrary,  the  powder  is  very  fine,  the  paste  very 
moist  and  compressed  very  strongly,  the  cupels  have  much  soli- 
dity, and  are  not  very  porous,  the  fine  metal  cannot  penetrate 
them,  and  the  operation  proceeds  very  slowly ;  besides,  the  assay 
is  likely  to  become  dulled  and  incapable  of  proceeding  without 
a  much  higher  degree  of  temperature  being  employed. — (Ber- 
thier.} 


312  MUFFLES. 

The  Process  of  Oupellation. — In  order  to  protect  the  cupel 
from  contact  with  the  fire,  and  at  the  same  time  allow  a  free 
access  of  the  air,  it  is  when  heing  heated  placed  in  a  muffle.    The 
muffle  is  a  refractory  vessel  of  baked  fire  clay,  Fig.  225,  arched 
above,  flat-bottomed,  and  pierced  near  its 
base  with  small  lateral  openings  for  the 
passage   of  the   heat.      Excepting    these 


I  x-^  ^~-<.^-^  \^  apertures,  and  that  at  the  front  for  the 
introduction  of  the  cupels  and  inspection  of 
the  process,  the  muffle  is  entirely  closed.  Its  dimensions  depend 
upon  the  size  of  the  cupel  and  of  the  furnace  in  which  it  is  to  be 
heated. 

Its  position  in  the  furnace  (D,  Fig.  1ST),  must  be  exactly  level, 
and  to  protect  it  from  the  corrosive  effects  of  volatilized  oxides, 
it  may  be  payed  over  with  a  thin  paste  of  bone-ashes.     The  muffle 
being  properly  arranged  in  the  furnace,  and  held  firmly  in  its 
place  by  lute,  the  cupels  are  then  introduced,  and  the  fuel  (char- 
coal) ignited.      The   lead  must  be 
Flg-  226>  perfectly  pure.     It  can  be  reduced, 

for   this   purpose,    from   refined   li- 
tharge.     "  When   the    cupels   have 
Fig  227.  been  exposed  for  half  an  hour,  and 

have  become  white  by  heat,  the 
lead  is  put  into  them  by  means  of 
the  tongs,  Fig.  226,  and  as  soon 

as  this  becomes  thoroughly  red  and  circulating,  as  it  is  called, 
the  metal  to  be  assayed,  wrapped  in  a  small  piece  of  paper,  is 
added,  and  the  fire  kept  up  strongly  until  the  metal  enters  the 
lead  and  circulates  well,  when  the  heat  may  be  slightly  dimi- 
nished, and  so  regulated  that  the  assay  shall  appear  convex  and 
ardent,  while  the  cupel  is  less  red, — that  the  undulations  shall 
circulate  in  all  directions,  and  that  the  middle  of  the  metal  shall 
appear  smooth,  surrounded  with  a  small  circle  of  litharge,  which 
is  being  continually  absorbed  by  the  cupel.  This  treatment 
must  be  continued  until  the  metal  becomes  bright  and  shining,  or 
is  said  to  i  lighten  ;  after  which,  certain  prismatic  colors,  or  rain- 
bow hues,  suddenly  flash  across  the  globules,  and  undulate  and 
cross  each  other,  and  the  latter  metal  soon  appears  very  brilliant 
and  clear,  and  at  length  becomes  fixed  and  solid.  This  is  called 


CUPELLATION   IN   TAYLOR'S  MUFFLE.  313 

the  '  brightening,  and  shows  that  the  separation  is  ended.  In 
conducting  this  process,  all  the  materials  used  must  be  accurately 
weighed,  especially  the  weight  of  the  alloy  before  cupellation, 
and  the  resulting  button  of  pure  metal.  The  difference  gives  the 
quantity  of  alloy." 

When  the  operation  is  completed,  the  cupel  is  to  be  withdrawn 
from  the  fire,  and  allowed  to  cool,  and  the  metallic  button  then 
removed  with  the  pincers.  If  the  assay  is  a  good  one,  it  will 
detach  easily.  The  button  should  be  round  and  brilliant  upon 
its  upper  surface,  but  rough  and  striated  at  the  bottom.  If  its 
surface  is  dull  and  flat,  too  much  heat  has  been  employed ;  on  the 
contrary,  when  it  is  spongy,  adheres  tenaciously  to  the  cupel, 
and  contains  scales  of  litharge,  there  has  been  a  deficiency  of 
heat,  and  the  fire  must  be  again  urged,  and  the  flowing  of  the 
metal  promoted,  by  adding  to  the  cupel  a  little  powdered  char- 
coal. Complete  fusion  is  indispensable  to  the  success  of  the  ope- 
ration. If  too  much  lead  has  been  added,  the  cupel  is  allowed 
to  cool,  the  button  carefully  separated,  so  as  to  be  free  from  adhe- 
rent particles  of  ash,  and  transferred  to  a  fresh  cupel  and  the 
process  continued.  In  experienced  hands,  the  pneumatic  blast, 
p.  169,  may  be  made  to  replace  the  furnace  in  the  process  of 
cupellation. 

Cupellation* in  Taylor  s  Muffle. — Mr.  T.  Taylor  (Memoirs  of 
Chem.  Soc.  vol.  iii.  p.  316),  claims  for  his  new  form  of  muffle 
the  following  advantages: — "1st.  Crucibles  may  be  maintained 
at  a  much  higher  temperature  than  can  be  readily  obtained  when 
the  ordinary  muffle  is  used,  while  the  degree  of  heat  and  the 
quantity  of  air  admitted  may  be  regulated  with  the  greatest 
nicety.  2d.  Owing  to  the  greater  draught  of  air,  the  oxidation 
of  the  lead  (in  the  process  of  cupellation)  is  more  quickly  effected ; 
and  lastly,  by  looking  through  an  opening  in  the  furnace  cover, 
the  operation  may  be  watched  from  first  to  last. 

"  Two  black  lead  crucibles  of  the  same  size  are  ground  flat,  so 
that  when  applied  one  to  the  other  they  may  stand  steady.  An 
oblong  or  semicircular  notch  is  cut  out  of  the  mouth  of  one  of  the 
crucibles,  and  a  hole  is  also  drilled  through  its  bottom.  This 
crucible,  when  placed  on  the  top  of  the  other,  constitutes  the 
muffle,  and  of  course  resembles  in  shape  a  skittle.  To  cupel 
with  this  apparatus,  the  lower  crucible  is  nearly  filled  with  clean 


314  SUBLIMATION — DISTILLATION. 

sand,  set  upon  the  bars  of  the  grate  in  the  centre  of  the  furnace, 
and  brought  to  a  low  red  heat.  The  cupel  containing  the  lead  of 
the  alloy  is  then  placed  upon  the  sand  and  immediately  covered 
by  the  crucible,  taking  care  that  the  notch  in  its  side  shall  be 
opposite  to,  and  correspond  with,  the  furnace  door ;  more  fuel  is 
added,  during  which  it  is  well  to  cover  the  hole  in  the  top  of  the 
muffle  with  a  crucible  lid,  in  order  to  prevent  the  admission  of 
dirt.  When  the  muffle  has  become  throughout  of  a  bright  red 
heat,  the  furnace  door  is  thrown  open,  and  the  ignited  fuel  gently 
moved  aside  so  as  to  permit  a  view  of  the  side-opening  in  the 
muffle.  The  current  of  air  which  is  thus  established  through  the 
muffle  instantly  causes  rapid  oxidation  of  the  lead,  and  this  may 
be  regulated  at  pleasure  by  closing  the  door  more  or  less.  If 
from  the  fuel  falling  down,  any  difficulty  should  be  experienced 
in  maintaining  a  free  passage  for  the  air,  a  portion  of  a  porce- 
lain tube,  or  a  gun-barrel,  may  be  passed  through  the  furnace 
door  to  within  an  inch  of  the  muffle ;  but  this  proceeding  is  gene- 
rally rendered  quite  unnecessary,  by  taking  care  to  place  some 
large  pieces  of  coke  immediately  round  the  door  of  the  furnace." 


CHAPTER  XVII. 

SUBLIMATION — DISTILLATION. 

WHEN  simple  or  compound  bodies  which  are  either  wholly  or 
in  part  capable  of  assuming  the  aeriform  state  are  subjected  to 
heat,  they  or  their  most  volatile  constituents,  upon  reaching  the 
required  temperature,  rise  in  the  form  of  vapor.  If  these  vapors, 
in  their  transit,  are  intercepted  by  a  surface  of  a  lower  tempera- 
ture, they  condense  and  take  a  solid  or  liquid  form,  according  to 
their  nature.  If  the  product  is  a  solid,  it  is  termed  sublimate, 
and  the  process  by  which  it  is  obtained  is  SUBLIMATION; — if  it  is 
liquid  or  gas,  it  takes  the  name  of  distillate,  and  the  operation 
which  yields  it  that  of  DISTILLATION. 

Both  of  these  processes  are  indispensably  useful  in  chemistry, 
for  they  afford  the  facility  of  taking  advantage  of  the  unequal 
volatility  of  bodies  for  their  separation. 


SUBLIMATION.  315 

As  instances  of  sublimation,  we  have  calomel  and  corrosive 
sublimate  made  by  heating  equivalent  proportions  of  sulphate  of 
mercury  and  common  salt ;  benzoic  acid  evolved  from  the  gum  ; 
pure  indigo  from  the  commercial  article,  and  camphor  from  the 
crude  material.  Iodine  is  sublimed  to  free  it  from  impurities ; 
biniodide  of  mercury  to  convert  it  into  crystals ;  naphthalin  to 
free  it  from  empyreumatic  matter,  and  succinic  acid  to  separate 
water. 

In  like  manner,  multitudes  of  instances  of  the  importance  of 
distillation,  in  the  everyday-processes  of  the  chemist  and  the  manu- 
facturer, might  be  adduced.  It  is  employed  in  the  separation  and 
rectification  of  alcohol,  the  preparation  of  the  ethers,  of  many 
mineral  and  vegetable  acids,  and  of  a  very  great  number  of  other 
chemical  products. 

SUBLIMATION. 

The  implements  of  sublimation  are  manifold,  and  vary  in  size 
and  construction  with  the  quantity  of  the  substance  to  be  heated, 
the  nature,  degree  of  volatility,  and  the  affinity  of  the  subliming 
body  for  the  oxygen  of  the  atmosphere. 

There  are  certain  rules  to  be  observed  in  order  to  a  successful 
execution  of  the  process ;  but  whatever  the  apparatus,  its  arrange- 
ment and  management  must  be  such  that  there  shall  be  no 
diminution  of  the  temperature  of  the  vaporized  matter  until  it 
reaches  the  recipient  in  which  it  is. to  be  refrigerated  and  con- 
densed. 

The  covers  of  flat  subliming  vessels  and  the  recipients  or 
condensing  portions  of  those  of  other  shapes,  must  invariably  be. 
out  of  and  above  the  fire,  and  exposed  to  the  cooling  influence  of 
air.  When  the  sublimed  particles  are  very  volatile,  it  will  even 
be  necessary  to  promote  their  condensation  by  covering  the 
recipient  with  rags,  which  are  to  be  kept  constantly  wet  with 
cold  water  or  some  other  refrigerant. 

The  usual  mode  of  heating  subliming  vessels  is  by  the  sand- 
bath,  but  for  some  substances  requiring  a  very  high  temperature 
for  their  volatilization,  direct  fire  is  necessary.  For  small  expe- 
riments, the  lamp  will  be  most  convenient;  but  in  large  opera- 
tions, the  furnace  must  be  used. 

In  order  to  prevent  explosion,  the  small  opening  in  the  top, 


316  SUBLIMATION   IN   TUBES. 

at  the  centre  of  the  refrigerant,  must  be  only  closed  with  a  plug 
of  raw  cotton,  and  should  be  freed  from  obstruction  by  occa- 
sional poking  with  a  wire.  When  the  escape  of  vapor  through 
this  hole  is^  rapid,  the  heat  is  too  high  and  must  be  diminished 
immediately. 

After  the  completion  of  the  operation,  the  apparatus  must  be 
left  to  cool  before  it  is  opened  or  the  recipient  removed. 

The  necessary  breaking  of  close  vessels  for  the  removal  of  the 
contents,  renders  their  use  expensive ;  whenever,  therefore,  the 
nature  of  the  substance  will  permit,  an  alembic  with  detached 
head  should  be  preferred.  Such  vessels  are  more  economical  and 
easy  of  management,  but  generally  require  that  their  joints  be 
made  impermeable  by  luting. 

Sublimation  in  Tubes.  —  Sublimation  is  very  available  in 
analyses  for  detecting  the  presence  of  minute  quantities  of  vola- 
tile metals,  acids,  and  other  substances,  the  implement  for  the 
purpose  being  a  small  tube  of  such  form  as  is  shown  in  Figs.  221, 
228.  After  the  introduction  of  the  substance,  previously  pow- 
dered and  dried,  the  tube  is  drawn  out  at  its  open  end  to  a  fine 
orifice,  and  the  lower  part  heated  gradually  over  the  flame  of  a 
spirit  lamp  (Fig.  228).  The  volatilized  portion  will  be  condensed 

upon  the  sides  of  the  upper  and 
cooler  parts.  By  dividing  the 
tube  with  a  file,  the  sublimate 
can  be  exposed  for  microscopic 
examination  or  removed  for  fur- 
ther assays  under  the  blow-pipe. 
The  tubes  for  sublimation  may 
be  from  4  to  8  inches  in  length, 
and  from  an  eighth  to  half  an 
inch  in  diameter,  according  to 

the  quantity  of  the  matter  to  be  sublimed,  and  the  required  deli- 
cacy of  the  operation. 

Berzelius  uses  a  tube  entirely  open  at  the  upper  end  for  those 
sublimations  in  which  there  are  two  volatile  products,  of  which 
one  is  to  be  drawn  off  entirely  in  the  form  of  gas  by  the  absorp- 
tion of  oxygen  from  the  atmosphere,  and  recognized  by  its  odor, 
and  the  other  condensed  in  the  upper  part  of  the  tube ;  as,  for 
example,  a  mixture  of  sulphur  and  selenium. 


SUBLIMATION   IN  FLASKS. 


317 


Fig.  229. 


Faraday  gives  the  form  of  a  tube  apparatus  (Fig.  229)  for 
condensing  heavy  vapors  or  easily  fusible 
substances,  as  naphthaline,  iodine,  &c. 
The  bent  tube  b  is  of  a  diameter  only  large 
enough  to  allow  its  free  passage  over  the 
subliming  tube  a.  The  upper  part  of  the 
middle  portion  of  the  tube  may  be  kept 
cool  by  paper  or  cloth  wrappers  moistened  with  water,  in  order 
to  promote  the  condensation  of  the  sublimed  matter.  The  heat 
of  the  spirit-lamp  is  sufficient  for  these  small  operations,  and  the 
apparatus,  as  adjusted,  may  be  properly  maintained  by  the 
upright  clamp,  Fig.  186. 

Sublimation  in  Flasks. — Florence  or  sweet  oil  flasks  are  well 
adapted  to  purposes  of  sublimation  on  account  of  their  cheapness, 
uniformity  of  thickness,  and  power  of  resisting  high  heats. 
Having  received  their  charge  they  are  to  be  imbedded  in  a  sand- 
bath  to  a  depth  above  the  level  of  the  contents,  and  heat  is  to  be 
applied  gradually  until  the  proper  temperature  is  arrived  at. 
The  position  of  the  flask  should  be  inclined,  so  that  its  neck  may 
lead  directly  into  the  recipient,  as  shown  at  Fig.  230.  In  this 
manner,  considerable  quantities  of  matter  may  be  operated  upon 
even  at  high  temperatures,  the  glass  bearing  a  red  heat  without 
injury.  Another  mode  of  arranging  a  flask  for  this  process  is  to 
connect  its  neck,  in  the  manner  of  a  hood,  with  a  long  bent  tube 


Fig.  230. 


Fig.  231. 


leading  into  the  refrigerant  and  recipient,  as  shown  in  Fig.  231. 
The  inconvenience  of  this  arrangement  is  the  condensation  of  the 
gaseous  matter  in  the  tube,  the  obstruction  from  which  may, 
without  great  care,  cause  the  explosion  of  the  flask. 

Flat  bottomed  flasks  of  thin  German  glass  are  sometimes  used, 


318 


SUBLIMATION   IN   RETORTS. 


Fig.  232. 


but  they  are  more  expensive  than  oil  flasks. 
Their  position  in  the  sand-bath  is  upright, 
and  the  flange  around  their  necks  acts  as  a 
support  for  an  inverted  globular  flask 
which  serves  as  a  recipient.  This  arrange- 
ment, shown  in  Fig.  232,  is  admirable  for 
the  sublimation  of  substances,  the  volatile 
products  of  which  are  so  aggregated  as  to 
form  what  are  called  flowers. 

Sublimation  in  Retorts. — Glass  retorts 
are  more  expensive  and  less  convenient 
than  flasks,  except  for  the  sublimation  of 
very  volatile  matters.  They  are  arranged 
as  shown  by  Fig.  238,  the  beak,  like  the 
neck  of  the  flask,  leading  into  a  wide- 
mouthed  receiver.  The  alembic,  Fig.  233,  is  frequently  substi- 
tuted for  retorts,  and  is  more  convenient,  as  its  head  being  de- 
tached from  the  body  allows  the  more  easy  removal  of  the 
sublimed  product. 


Fig.  233. 


Fig.  234. 


Earthenware  retorts  with  loose  heads,  Fig.  234,  to  be  fastened 
by  pins  and  lute,  are  employed  for  sublimations  requiring  high 
temperatures. 

Sublimation  in  Crucibles. — The  crucible  for  this  purpose  may 
be  of  clay,  platinum,  or  iron,  according  to  the  nature  of  the  sub- 
stance to  be  heated.  It  is  first  coated  with  a  layer  of  refractory 


SUBLIMATION   IN    SHALLOW   VESSELS.  319 

clay  paste,  and  when  this  is  dry,  placed  over  a  furnace  fire.  An 
inverted  crucible  of  the  same  size  with  a  small  hole  in  its  top,  is 
then  placed  over  as  a  recipient  of  the  vaporized  particles.  The 
top  crucible  must  be  above  and  out  of  the  fire.  When  the  opera- 
tion is  finished,  and  the  apparatus  has  cooled,  the  top  may  be 
removed  and  the  crucible  emptied  of  its  contents. 

Sublimation  in  Shallow  Vessels. — In  the  treatment  of  sub- 
stances which  sublime  at  a  low  heat,  a  plate  or  capsule  resting 
upon  hot  sand  and  surmounted  by  a  glass  funnel  or  a  cone  of 
glazed  paper,  as  a  condenser  and  recipient,  answers  every  pur- 
pose, particularly  in  the  sublimation  of  organic  substances.  The 
top  of  the  funnel  and  cone  should  be  drawn. out  to  a  small  open- 
ing, and  when  the  operation  is  finished  the  contents  of  the  refri- 
gerant may  be  removed  by  a  feather. 

When  iron  capsules  are  used,  as  is  often  necessary  in  sublima- 
tions requiring  high  heat,  they  should  be  lined  with  a  thick  dough 
of  fire  clay.     Capsules  with  flat  bottoms  and  of  thick  sheet  iron 
are  most  appropriate.     Their  dimensions  may  be  six  inches  in 
diameter,  and  J  to  1  inch  in  depth.     The  top  B  must  be  of  earthen^ 
ware  and  detached.    The  arrange- 
ment is  shown  in  Fig.  235.     This  Fis-  235- 
implement  requires  a  furnace  heat.       ^— £-~^  B  « 
The  cover  should  be   tightly  ce-      ^            •/'     ^"^^~~~^     U 
rnented  with  fire  lute,  and  when 

the  whole  has  cooled,  the  cover  may  be  taken  off  and  the  adhe- 
rent mass  of  sublimate  removed  with  a  spatula.  The  small  cone 
c  is  to  be  kept  over  the  hole  in  the  cover  to  arrest  any  escaping 
vapors.  When  it  is  necessary  to  probe  the  cavity,  it  may  be 
temporarily  removed  with  the  tongs. 
A  diaphragm  of  porous  white  paper  Flg-  236< . 

will  arrest  the  passage  of  any  empy- 
reumatic  matter,  and  pass  the  subli- 
mate free  from  color. 

Two  very  concave  watch-glasses, 
placed  the  one  upon  the  other  with 
their  convex  surfaces  outward,  make 
a  very  neat  subliming  apparatus  for 
minute  quantities  of  rare  matter. 

Flat  vessels,  with  tall  conical  caps,  Fig.  236,  are  also  made  of 
biscuit  and  earthenware  for  subliming  operations. 


320 


IIYDRO-SUBLIMATIOX. 


Ures  Apparatus. — This  is  a  very  convenient  arrangement, 
Fig.  237,  consisting  of  two  metallic,  glass,  or  porcelain 
Fig.  237.  ygggeig.  The  lower  one  is  the  recipient  of  the  matter 
to  be  sublimed,  and  the  upper  #,  which  is  the  larger, 
covers  the  former,  and  is  to  be  filled  with  cold  water, 
to  be  replaced  as  fast  as  it  evaporates.  When  the  pro- 
cess is  completed,  the  sublimed  matter  can  be  removed 
from  the  exterior  of  the  cover. 

Henry's  Apparatus  for  Hydro- Sublimation. — This  arrange- 
ment, shown  in  Fig.  238,  has  been  proved  by  experience  to  be 

*  ,*•  Fig.  238. 


practically  useful.  It  is  employed  in  manufacturing  laboratories 
for  the  sublimation  of  calomel,  but  is  equally  applicable  for  other 
substances ;  and,  by  lessening  the  dimensions  of  the  several  pieces, 
may  be  made  very  convenient  for  experimental  purposes. 

It  consists  of  a  large  globular  glass  vessel  a,  with  a  long 
straight  neck,  and  two  short,  lateral  tubulures  of  equal  width. 
For  manufacturing  purposes  the  globe  must  be  of  stoneware,  and 
of  two  or  more  gallons  capacity.  In  either  case  it  rests  upon 
the  ledge  of  a  blue  stone-ware  cylinder  A,  containing  sufficient 
water  to  close  the  neck  of  the  globe,  which  dips  lightly  into  it. 
One  of  the  tubulures  receives  the  neck  of  the  retort  6,  and  the 
other  that  of  the  still,  Fig.  25,  which  furnishes  the  steam,  or, 
what  is  better,  a  conduit  pipe  from  the  generator,  Fig.  13  or  14. 
The  retort  6,  of  earthenware,  or  iron,  coated  interiorly  with  fire 
clay,  is  for  the  evolution  of  the  calomel  or  sublimate  in  vapors. 
It  is  wholly  enclosed  in  the  furnace,  and  its  very  short  neck  passes 


HYDRO-SUBLIMATION. 


321 


Fig.  239. 


immediately  from  it  into  the  globe  a,  so  as  to  prevent  the  con- 
densation of  the  sublimate  in  the  neck  and  upper  portion.  The 
joints  should  be  tightly  luted.  The  success  of  the  operation  de- 
pends mainly  upon  a  proper  management  of  the  fire  and  supply 
of  aqueous  vapor.  The  heat  should  be  just  sufficient  to  drive 
over  the  sublimate  slowly,  and  the  steam  should  be  supplied  in 
large  excess,  and  simultaneously  with  the  appearance  of  the 
vaporized  solid.  For  this  purpose  the  steam-conduit  must  be 
fitted  with  a  cock  for  the  regulation  of  the  flow  of  its  contents  of 
vapor.  As  soon  as  the  sublimed  mole- 
cules come  in  contact  with  the  aqueous 
vapor,  they  are  condensed  in  the  globe  a, 
and  precipitate  as  powder  (p.  100)  into  h. 

By  increasing  the  size  of  the  globe 
a,  threefold,  diminishing  the  orifice  of 
its  neck  by  means  of  a  small  glass 
tube  passing  through  a  perforated  cork, 
and  by  omitting  the  tubulure  on  the  other 
side,  the  steam  may  be  dispensed  with 
for  the  sublimations  of  volatile  solids  into 
flowers.  The  neck  in  this  case  must  point 
upwards. 

For  experimental  operations,  a  small  earthenware  retort  and 

Fig.  240. 


glass  globe  will  answer  every  purpose.     The  steam  can  be  sup- 

21 


322  DISTILLATION. 

plied  from  the  copper  washing  bottle,  Fig.  240,  by  substituting 
for  the  spirting  tube  d,  a  flexible  leaden  pipe  <?,  which  is  to  be 
connected  with  the  neck  of  the  flask  by  a  coupling-screw  a.  The 
gas  or  spirit  lamp  will  furnish  ample  heat  for  the  generation  of 
steam  in  this  apparatus. 

DISTILLATION. 

A  process  by  which  substances  are  heated  for  the  separation 
of  a  volatile  from  a  more  fixed  portion.  The  apparatus  for  the 
purpose  consists  of  a  close  vessel  in  which  the  heating  takes 
place,  a  refrigerant  for  the  condensation  of  volatilized  particles, 
and  a  recipient  for  the  retention  of  the  product ;  the  two  latter 
purposes  being  often,  however,  fulfilled  by  the  same  vessel. 
When  this  product  condenses  as  a  fluid,  the  process  takes  the 
name  of  liquid  distillation,  and  if  as  a  gas,  of  gaseous  distilla- 
tion. The  subjection  of  a  body  to  very  high  heat,  for  the  pur- 
pose of  decomposing  it  and  receiving  the  generated  products,  is 
called  dry  or  destructive  distillation.  In  SUBLIMATION,  which 
may  be  styled  solid  distillation,  the  volatilized  matter  is  received 
and  condensed  in  one  vessel  without  the  necessity  of  an  interme- 
diate refrigerant. 

The  process  of  distillation  is  one  of  the  most  indispensable  in 
chemical  investigation,  as  by  its  aid  we  can  not  only  separate 
liquids  of  different  volatility,  but  also  collect  new  volatile  pro- 
ducts which  may  result  from  the  decomposition  of  single  or  mixed 
substances.  As  instances  of  its  valuable  use,  we  can  by  its  aid 
separate  the  essential  oil  and  volatile  constituents  of  plants  and 
of  other  materials, — recover  alcohol,  ether,  or  any  valuable  vola- 
tile liquid,  from  solutions  in  which  they  are  solvents, — refine  a 
liquid  from  its  fixed  impurities, — free  it  from  fixed  matter  which 
it  may  have  in  solution,  and,  aided  by  an  absorbent  material, 
remove  any  contained  water.  Moreover,  it  allows  the  collection, 
either  free  or  in  solution,  of  gases  generated  by  chemical  re- 
action. .^ 

The  Still. — The  still  is  the  common  implement  used  in  large 
operations  of  liquid  distillation.  It  is  generally  made  of  copper, 
and  is  tinned  internally.  A  convenient  form  has  already  been 
fully  described  at  page  52.  The  following  figure  exhibits 
another  of  handsomer  appearance,  but  constructed  upon  similar 


THE    STILL. 


323 


principles.  It  is  mounted  in  brickwork,  but  can  as  readily  and 
with  as  good  results,  have  its  position  in  the  more  economical  iron 
cylinder,  Fig.  24. 

Fig.  241. 


By  way  of  illustrating  the  necessary  manipulations,  we  will 
describe  the  different  steps  of  the  operation  as  commonly  per- 
formed. 

The  substance  to  be  distilled  is  placed  in  the  body  A,  the 
pewter  or  tinned^  copper  head  c,  is  luted  on  and  adjusted  to  the 
pewter  worm  B,  and  the  fire  is  lighted  in  the  furnace.  To  insure 
facility  of  management,  the  several  parts  of  the  arrangement 
should  be  made  to  fit  accurately  to  each  other.  As  the  heat 
increases,  the  contents  of  the  body  or  cucurbit  begin  to  boil,  and 
that  portion  volatilizable  at  the  temperature  of  the  applied  heat 
mounts  in  vapor  to  the  head  or  capital  c,  there  partially  con- 
denses, runs  into  the  beak  or  neck  D,  and  ultimately  into  the 
spiral  worm  E  B,  where,  together  with  any  uncondensed  vapor,  it  is 
liquefied  and  cooled  by  the  surrounding  water  previous  to  its  exit 
into  the  recipient  P,  which  may  be  an  open  pan  if  the  product  is 
not  volatile,  and  a  glass  bottle  or  carboy  if  it  is.  The  cooler 
I  j  K  L,  in  which  the  worm  is  immersed,  consists  of  a  wooden 
cistern  filled  with  water,  which  requires  to  be  constantly  cool, 
and  therefore  must  be  frequently  renewed.  For  this  purpose, 
there  is  a  conduit  N  M  attached,  which  receives  cold  water  from 
the  hydrant  pipe  R,  and  conveys  it  in  a  constant  stream  to  the 
bottom  of  the  cistern,  so  that  it  may  displace  the  heated  water, 


324 


THE   COOLER. 


which  has  become  lighter  by  expansion,  through  the  lateral  out- 
let at  the  top.  This  water,  already  heated,  can  be  more  econo- 
mically used  for  making  distilled  water  than  when  cold,  as  it 
takes  less  fire  to  boil  it  when  transferred  to  the  still.  If  the 
cistern  is  kept  clean,  it  makes  an  excellent  reservoir  for  the 
supply  of  hot  water  to  the  laboratory,  as  the  still  is  frequently  in 
use  for  making  distilled  water,  and  for  other  purposes. 

When  fresh  additions  of  liquid  are  to  be  made  they  can  be 
poured  through  the  tubulure  A.  This  saves  the  trouble  of  taking 
off  the  head  of  the  apparatus,  which  need  only  be  removed  after 
the  completion  of  the  operation  for  the  purpose  of  cleaning  the 
still  and  its  parts.  As  the  residuum  is,  in  many  instances,  as 
much  the  object  of  the  process  as  the  distillate,  it  must,  when 
such  is  the  case,  be  carefully  removed  from  the  still,  and  trans- 
ferred to  a  suitable  vessel  for  preservation  or  further  reaction. 

The  size  of  the  still  varies  with  the  amount  of  material  to 
be  operated  upon.  For  the  ordinary  purposes  of  the  labora- 
tory it  need  not  exceed  fifteen  gallons  capacity.  It  must  be 
proportioned  so  as  to  have  as  much  heating  surface  as  possible, 
while,  at  the  same  time,  its  height  is  sufficient  for  the  foaming 
and  frothing  of  its  contents  without  danger  of  their  boiling  over 
into  the  neck. 

We  have  described  a  spiral  worm,  because  that  is  the  usual 
form  of  refrigerants,  an  important  point 
in  the  construction  of  which  is  to  pro- 
vide as  much  cooling  surface,  and  conse- 
quently as  great  a  length  of  pipe  as  pos- 
sible in  a  small  space.  Schrader's  con- 
denser, Fig.  242,  which  is  preferred  by 
some  manufacturers,  because  more  easily 
cleaned,  consists  of  a  metallic  ball,  the 
upper  part  of  which  projects  above  the 
water  contained  in  the  cooler.  From  the 
lower  side  of  this  ball  three  straight  tubes 
proceed,  and  conduct  the  vaporized  par- 
ticles downwards  into  the  exit  tube  with 
which  they  connect.  The  exit  tube  is 
closed  at  its  upper  end  with  a  cock,  and 
open  at  the  other  for  the  escape  of  the  condensed  liquid.  Gedda's 


Fig.  242. 


DISTILLATION  IN   RETORTS.  325 

condenser,  already  given  at  p.  48,  is  still  more  convenient  than 
either  of  the  two  preceding. 

Whatever  the  form  of  the  refrigerant,  its  mode  of  action  is  the 
same.  It  is  constructed  so  as  to  facilitate  as  much  as  possible 
the  perfect  and  rapid  condensation  of  the  enclosed  vapors.  The 
greater  the  amount  of  surface  which  it  presents  to  the  water,  the 
more  effectual  its  action ;  for  the  sooner  the  heat,  absorbed  by  the 
distillate  in  assuming  the  gaseous  form,  is  abstracted  by  the  sur- 
rounding water,  the  more  rapidly  it  becomes  condensed  and 
cooled.  The  condensation  may  be  hastened  by  surrounding  the 
recipients  with  a  frigorific  mixture,  which,  if  the  vessel  be  of 
glass,  must  be  at  first  applied  gradually,  lest  its  too  sudden  cool- 
ing causes  its  fracture. 

Volatile  liquids  are  distilled  by  the  heat  of  BATHS  ;  and  for 
those  liquids  which  corrode  metals,  a  stoneware  still  must  be 
used. 

Distillation  in  Retorts. — Retorts  are  egg-shaped  vessels,  an- 
swering a  more  convenient  purpose  than  the  still  in  the  nicer 
distillatory  operations.  They  are  mostly  of  glass,  but  for  some 
processes  those  of  porcelain,  earthen  and  stoneware,  platinum 
and  iron,  are  necessary.  Retorts  are  also  used  in  technical  ope- 
rations, and  the  laboratory  should  be  supplied  with  a  series 
ranging  from  those  of  a  half  ounce  up  to  several  gallons  capa- 
city. Glass  retorts  should  be  made  of  hard,  white  glass,  free 
from  lead.  Those  of  German  crown-glass  are  very  thin,  but  of 
uniform  thickness  and  of  sufficient  strength,  and  moreover  with- 
stand both  high  temperatures  and  the  corrosive  action  of  acids 
and  alkalies.  The  surface  must  be  perfectly  smooth  and  free 
from  blur  or  striae. 

Some  judgment  is  required  in  the  selection  of  retorts.  One 
properly  constructed  is  exhibited  in  Eig.  243.  It  is  seen  that 
the  neck  proceeds  laterally  from  the  summit  of  the  body,  forming 
a  wide  tube  at  its  origin,  which  tapers  gradually  into  a  narrow 
beak.  The  arch  of  the  retort  should  be  so  fashioned  as  to 
reverberate  any  particles  of  boiling  matter  that  may  spirt  up- 
wards against  it,  and  thus  prevent  their  overflow  into  the  beak. 
A  large  neck  facilitates  the  process,  because  it  allows  more  room 
for  the  accumulation  of  vaporized  matter,  and  presents  a  propor- 
tionally less  surface  to  the  cooling  influence  of  the  atmosphere. 


326 


DISTILLATION  IN   RETORTS. 


It  is  very  essential  that  the  curve  between  the  neck  and  the 
body  #,  Fig.  243,  should  be  so  formed  as  to  make  the  straight 
line  a  b  form  an  obtuse  angle,  with  the  dotted  line  b  a.  If,  on 
the  contrary,  it  is  made  as  shown  by  Fig.  244,  which  presents  the 

Fig.  243. 


Fig.  '244. 


Fig.  245. 


usual  form  of  those  sold  in  the  shops,  the  vapors,  condensing  in 
the  arch  as  far  as  the  dotted  line  a  6,  fall  back  again  into  the 
body,  whilst,  in  Fig.  243,  the  dividing  line,  from  which  the  dis- 
tillate commences  to  flow,  is  much  nearer  to  the  body.  So  that 
a  retort  like  Fig.  243,  will  distil  twice  as  rapidly  as  another 
similar  to  Fig.  244,  which,  however,  when  it  has  the  form  shown 
by  the  dotted  lines  c  d  a,  becomes  equally  convenient. 

The  pear-shaped  retort,  Fig.  248,  being  deeper  in  the  body 
or  bulb,  is  better  fitted  for  distilling  volatile  substances,  and 
others  which  foam  and  swell  upon  being  heated.  The  globular 
form,  Fig.  245,  presents  less  depth,  but  more  heating  surface, 
and  is,  therefore,  better  adapted  to  those  liquids  which  boil 
quietly  and  distil  more  slowly. 

A  great  improvement  to  the  plain  retort,  is  the  addition  of  a 
glass  stoppered  tubulure  to  the  neck,  as  at  Fig.  245.  The  tubu- 
lure  should  have  its  position  exactly  as  shown  in  the  cut,  so  that 
the  vapors  condensing  about  it  may  flow  back.  Tubulated  retorts 
are  preferable,  because  they  are  more  readily  cleansed  and 
charged  than  those  of  plain  shape ;  moreover,  they  admit  of  fresh 


DISTILLATION   IX    RETORTS. 


327 


additions  to  their  contents  without  the  necessity  of  disturbing 
the  arrangement. 

The  vessels  into  which  the  distillate  from  the  retorts  passes  are 
technically  termed  receivers.  Fig.  246.  They  should  be  of  glass, 
except  in  a  few  special  cases,  and  always  free  from  lead ;  care 
being  observed,  at  the  same  time,  to  select  those  which,  while 
thick  enough  for  strength,  will  be  sufficiently  thin  to  bear  sudden 
changes  of  temperature.  The  usual  shape  is  that  of  a  globe  with 

Fig.  246. 


a  neck,  widening  gradually  towards  the  mouth,  for  the  reception 
of  the  tapering  ends  of  the  retorts. 

To  render  them  available  for  connection  with  other  apparatus 
besides  the  retort,  as  shown  by  A,  Fig.  246,  they  are  often  fitted 

Fip.  247. 


with  tubulures.     In  rare  cases,  the  long  neck  tube  is  replaced  by 
a  tubulure.     The  interior  of  the  tubulures  should  be  perfectly 


328 


DISTILLATION   IN   RETORTS. 


round  and  smooth,  so  that  corks  may  be  tightly  fitted  in  them 
according  to  necessity. 

If  the  distillation  is  to  be  urged  over  an  Argand  lamp,  the 
neck  of  the  receiver  to  be  attached  to  the  retort  should  be  long, 
and  the  connection  made  by  inserting  the  beak  of  the  latter  in 
its  mouth.  Fig.  247,  and  by  rendering  the  joint  air-tight  with  a 
wrapper  of  india-rubber  cloth,  as  shown  at  R  in  the  figure.  The 
funnel  D  is  charged  with  water,  which  flows  in  a  thin  stream, 
regulated  by  the  cock  in  the  barrel,  upon  the  receiver,  covered 
with  sponge  or  bibulous  rags,  and  resting  in  a  capsule  c. 

If  the  retort  is  to  be  heated  in  a  furnace,  the  junction  of  the 
beak  with  the  tubulure  of  the  receiver  is  tightened  by  means  of  a 
perforated  cork  through  which  the  beak  passes,  and  sealed,  if 
necessary,  by  a  coating  of  flaxseed  and  whiting  lute,  as  shown 
at  R,  Fig.  248.  The  receiver  B,  resting  upon  a  straw  ring  in 

Fig.  248. 


a  wooden  pail,  is  cooled  by  a  stream  of  water  from  the  hydrant 
pipe  ij  which,  as  it  becomes  warm,  flows  off  into  the  funnel  d 
leading  into  the  drain. 

In  order  to  increase  the  surface  of  the  beak,  and  consequently 


249. 


to  facilitate  the  liquefaction  of  the  vapors  passing  through  it  into 
the  receiver,  there  is  often  placed  between  the  beak  of  the  retort 


DISTILLATION  IN  RETORTS. 


329 


and  the  tubulure  of  the  receivers,  but  connected  with  both,  an 
adapter,  Fig.  249.  This  is  a  pointed  conical  tube  of  white  glass, 
free  from  lead,  which,  when  leading  from  a  condenser  to  a  bottle, 

Fig.  250. 


takes  a  bent  form,  as  shown  at  A  in  the  same  figure.  Fig.  251 
exhibits  a  complete  arrangement  of  a  distillatory  apparatus,  com- 
bining a  tubulated  retort  with  an  s  tube,  an  adapter,  a  recipient 
placed  in  a  vessel  with  a  constant  stream  of  cold  water  flowing 
into  it,  and  a  syphon-tube  with  a  second  receiver.  The  curved 
adapter  is  needed  where  the  receiver  rests  vertically  instead  of 
horizontally. 

As  it  is  requisite  frequently,  in  distilling  volatile  liquids,  to 
have  a  larger  extent  of  cooling  surface  than  is  presented  by  the 
globular  receiver,  another  form  has  been  devised  by  Liebig,  which 
is  very  convenient.  It  consists  of  a  glass  tube  «,  25  to  30  inches 
long  and  two  inch  bore,  connected  with  the  beak  of  the  retort, 
and  running  through  a  sheet  brass  cylinder  ft,  of  20  inches  in 
length  and  two  or  more  inches  diameter.  The  metal  tube  is 
closed  at  each  end  with  perforated  corks,  through  which  the  glass 
rod  passes,  and  is  held  in  a  central  position.  A  constant  stream 
of  cold  water,  supplied  through  the  funnel-tube  <?,  passes  into  the 
cylinder,  surrounds  the  glass  tube,  condenses  the  vapor  therein 
contained,  and,  becoming  warm,  passes  out  through  the  exit  pipe 
d,  to  give  place  to  cooler  water.  The  figure  below  exhibits  one 


330 


DISTILLATION   IN   TUBES. 
Fig.  251. 


mounted  upon  an  iron  stand,  with  joint  and  sliding  rod ;  from 
which,  for  small  operations,  it  may  be  detached  and  supported 
by  a  wooden  clamp. 

Fig.  252. 


For  micro-chemical  distillations,  the  necessary  apparatus  may 
be  formed  of  glass  tubes  blown  into  proper  shape  over  the  blow- 
pipe table.  Fig.  252  exhibits  Clarke's  tube  retort  and  receiver  : 
a  the  retort,  of  an  ounce  capacity ;  b  the  receiver,  8  by  three 


PLATINUM  RETORTS.  331 

X 

quarter  inches,  and  c  the  distilled  liquor.     The  junction  of  the 
retort  and  receiver  (d)  should  be  hermetical. 

Plain  bulbs  a,  and  tubulated  £,  Fig.  253,  are  other  forms : — 
the  tube  b  of  the  latter  serves  for  the 
suction  of  the  liquor  to  be  heated,  and 
may  afterwards  be  sealed  in  the  flame  of 
a  spirit-lamp. 

The  means  of  heating  these  small  ves- 
sels, are  the  small  spirit-lamps,  Figs.  151, 
152,  except  when  it  is  required  to  modify 
the  heat  by  the  intervention  of  a  sand- 
bath,  which  requires  a  larger  lamp.  The 
clamp  supports,  p.  186,  heretofore  described,  are  of  very  great 
convenience  in  the  adjustment  of  these  tube  arrangements. 

A  simpler  form  of  tube  retort  is  shown  in  Fig.  254.     It  is 

Fig.  254. 


readily  made  by  closing  a  tube  at  one  end  and  bending  it  in  a 
zigzag  direction,  as  represented  in  the  drawing.  The  liquid  to 
be  distilled  is  at  #,  and  the  recipient  at  b.  To  render  it  appli- 
cable to  the  generation  and  collection  of  gases,  the  tube  may  be 
drawn  out  at  its  open  end  and  bent  downwards,  if  necessary,  to 
reach  the  receiver, 

Platinum  Retorts. — The  size  of  these  vessels  varies  from  a 
quart  down  to  an  ounce,  these  capacities  being 
adapted  to  all  the  purposes  of  an  analytic  Fig.  255. 

and  pharmaceutic  laboratory.  The  usual 
form  is  shown  in  Fig.  255.  The  body  a  is 
nothing  more  than  a  stout  crucible  with  a 
thick  rim  d.  The  head  b,  with  the  helm  <?, 
should  be  hammered  from  one  piece,  or  else 
very  closely  welded  together,  and  it  should  be 
ground  at  its  rim  so  as  to  fit  perfectly  to  the  mouth  of  the  still. 

Platinum  stills  are  very  useful  for  destructive  distillation,  for 
determining  the  amount  of  matter,  if  any,  lost  by  substances  at 


332 


IRON   RETORTS. 


a  red  heat,  for  the  distillation  of  matters  not  readily  volatilized, 
of  those  which  corrode  glass,  &c.,  and  consequently  as  a  substi- 
tute for  lead  in  the  preparation  of  fluohydric  acid. 

Those  of  a  large  size  should  be  fitted  with  handles,  so  as  to 
diminish  their  liability  to  defacement  by  transfer  from  place  to 
place.  When  heated  over  charcoal,  they  should  be  well  payed 
over  with  an  external  coating  of  fire-clay  paste.  Otherwise,  the 
directions  for  using  the  platinum  still  are  the  same  as  those 
given  for  the  crucible  at  p.  283.  The  gas  or  spirit  lamp  will 
furnish  the  amount  of  heat  required  for  most  operations. 

Iron  Retorts. — All  iron  retorts  may  be  of  cast  metal.  A 
very  neat  form  for  small  operations  is 
shown  by  Fig.  256.  A  simpler  and  more 
economical  apparatus  is  a  mercury  flask, 
with  an  iron  gas  tube  or  gun  barrel 
screwed  into  the  top,  and  reaching  nearly 
to  the  bottom,  and  another  tube  bent 
downwards.  This  arrangement,  well 

fitted  for  distilling  dry  substances  which  require  a  high  heat, 
may  be  modified  by  removing  the  centre  pipe  and  inserting  a 
screw-plug,  and  thus  be  made  well  adapted  to  the  distillation  of 
mercury.  For  distilling  naphtha,  caoutchicine,  and  similar  sub- 
stances, the  usual  form  of  a  glass  retort  is  sometimes  preferred. 

Fig.  257. 


Fig.  256. 


Fig.  257  exhibits  an  iron  crucible  retort,  with  a  cover,  which 
is  held  close  to  the  body  by  means  of  a  clamp,  when  the  retort 
is  in  operation.  A  bent  gas-tube  carries  off  the  distillate  into  a 
receiver. 

Plate  iron  retorts,  sometimes  used  for  the  generation  of  gases 


GENERAL  RULES  FOR  DISTILLATION.  333 

by  high  heat,  are  referred  to  in  the  distillation  of  volatile  sub- 
stances. 

All  of  these  iron  retorts  are  heated  in  furnaces.  When  not 
in  use,  they  should  be  greased  to  prevent  oxidation,  and  should 
be  kept  stoppered.  One  per  cent,  of  platinum,  it  is  said,  renders 
iron  resistant  to  acid  and  corrosive  liquids. 

Porcelain  Retorts. — These  implements,  of  shape  similar  to 
those  of  glass,  are  only  used  for  dry  distillations ;  but  being 
fragile,  require  to  be  very  carefully  heated.  Being  opaque,  they 
have  not  the  advantage  of  glass,  which  allows  the  inspection  of 
the  contents  of  the  vessel. 

Earthenware  and  Stone  Retorts. — The  application  of  this  ware 
to  the  purposes  of  distillation  is  very  limited.  To  render  it  im- 
permeable by  gases,  the  retorts  should  be  wet  with  a  solution  of 
borax,  or  else  payed  over  with  a  coating  of  paste  made  from  9 
parts  of  clay  and  1  part  of  powdered  borax,  and  then  heated  to 
fusion  and  gradually  cooled.  The  usual  form  is  that  of  the  glass 
retorts. 

Q-eneral  Rules  for  Distillation. — In  the  distillation  of  sub- 
stances which  require  a  high  heat,  the  vessel  may  be  placed  over 
the  naked  fire.  If  it  is  a  metallic  still,  the  cylinder,  Fig.  24, 
affords  every  convenience  for  heating  by  this  method.  The  uni- 
versal furnace,  Fig.  134,  is  the  proper  heating  implement  for 
earthen  and  metallic  retorts ;  and  the  spirit  or  gas  lamp  for  those 
of  glass  and  porcelain.  When  the  nature  of  the  process  requires 
a  modification  of  the  heat,  it  can  be  accomplished  by  means  of 
intermediate  BATHS,  which  will  furnish  any  temperature  required 
up  to  the  boiling-point  of  the  medium  employed. 

Glass  and  porcelain  retorts  should,  if  possible,  never  be  heated 
over  the  naked  fire,  because  of  their  great  liability  to  fracture. 
The  impossibility  of  maintaining  a  uniform  heat  is  a  serious 
objection  to  this  mode,  for  the  ebullition,  though  rapid,  is  not 
uniform.  When  it  is  necessary  to  use  the  naked  fire  for  glass 
and  porcelain  retorts,  the  same  directions  are  applicable  to  their 
management  as  to  that  of  earthen  or  metallic  retorts,  though  in 
the  use  of  the  latter  less  care  is  requisite.  The  proper  position 
of  the  retort  is  in  the  centre  of  the  furnace,  Fig.  238,  upon  a 
crow-foot  or  support,  Fig.  43,  resting  on  the  grate.  The  retort 


334  GENERAL   RULES    FOR   DISTILLATION. 

having  been  previously  charged,  its  beak  is  then  adapted  to  the 
receiver,  and  the  joints  closed  by  lute.  A  very  small  fire  is  then 
ignited  and  increased  as  the  retort  has  become  warm,  till  it 
reaches  to  within  a  line  or  two  of  the  level  of  the  contained 
liquid.  If  the  coals  project  beyond  this  point,  the  surface  of  the 
dry  or  upper  part  of  the  retort  acquires  a  temperature  so  much 
higher  than  that  of  the  substance  which  is  being  heated,  that  the 
difference  may  cause  its  fracture  when  particles  are  projected 
against  it.  A  certain  degree  of  heat  in  the  upper  part  of  the 
vessel  is,  however,  necessary,  so  that  the  opposite  condition — the 
condensation  of  vapor  in  it, — may  not  occur ;  and  where  the  retort 
is  heated  unequally,  it  is  sometimes  necessary  to  place  over  it  the 
dome  of  the  furnace.  For  the  same  reason,  also,  when  a  retort 
is  heated  over  a  spirit  or  gas  lamp,  or  by  any  other  way  in  which 
the  upper  portion  is  exposed,  that  part  should  be  covered  with  a 
dome.  Fig.  258  exhibits  such  a  one  of  earthenware  for  large 
retorts.  A  cone  of  pasteboard,  Fig.  259,  will  answer  better  for 

Fig.  258.  Fig.  259. 


smaller  vessels.  The  notch  in  the  front  allows  its  adaptation  to 
the  neck  ;  but  while  adjusted  so  as  to  effectually  protect  the  upper 
part  of  the  retort  from  contact  with  air,  it  must  be  supported  in 
such  a  manner  that  its  weight,  when  great,  shall  not  endanger 
the  safety  of  the  retort. 

The  addition  of  the  fuel  should  be  gradual,  so  that  the  fire 
may  be  only  sufficient  to  gently  boil  the  contained  liquid.  The 
coals  should  be  first  ignited  to  expel  moisture  ;  and  when  the 
operation  is  nearly  completed,  the  fire  must  be  skilfully  managed. 
For  greater  safety,  the  glass  retorts  should  always  be  coated  ex- 
teriorly with  a  paste  of  refractory  clay,  or  enveloped  at  the 
lower  part  with  wire  gauze. 


DISTILLATION   OF  LIQUIDS.  335 

When  the  Argand  or  gas  lamp  is  used  as  the  means  of  heating^ 
the  retort  need  only  be  arranged  upon  a  support  and  brought 
over  the  flame,  which  is  to  be  applied  gradually  at  first,  and 
slowly  elevated  until  the  glass  has  become  heated  throughout. 
To  diffuse  the  heat  and  prevent  the  direct  contact 
of  the  flame,  the  ring  of  the  support  upon  which  Fig-  26°- 
the  retort  rests,  should  have  a  wire  gauze  bowl, 
Fig.  260,  for  the  holder. 

Fig.  248  exhibits  a  retort  properly  located  in  a 
SAND-BATH,  this  being  the  mode  of  heating  retorts 
for  the  distillation  of  volatile  liquids,  such  as  ethers  and  the  like. 
The  advantage  of  the  sand-bath  over  the  naked  fire  for  heating 
glass  retorts,  particularly  those  of  large  size,  is  that  it  imparts  a 
more  uniform  degree  of  heat,  and  prevents  the  possibility  of 
fracture  from  sudden  changes  of  temperature.  The  sand  should 
be  fine,  and  the  layer,  upon  which  the  bottom  of  the  retort  rests, 
about  an  inch  or  two  deep,  according  to  the  size  of  the  retort. 
The  sand  surrounding  the  retort  should  only  reach  to  the  level 
of  the  contained  liquid,  and  should  be  removed  gradually  as  it 
evaporates. 

To  prevent  condensation  in  the  top,  the  upper  portion  of  the 
retort  may  sometimes  be  advantageously  covered  with  a  woollen 
cloth. 

When  the  operation  is  performed  with  a  view  to  separate  two 
liquids  which  boil  at  different  temperatures,  the  retort  must  be 
either  set  in  a  bath  which  does  not  exceed  the  temperature  at 
which  the  more  volatile  liquid  escapes ;  or  else,  when  otherwise 
heated,  the  temperature  must  be  regulated  by  a  glass  thermo- 
meter, Fig.  120,  entering  the  retort  through  its  tubulure,  and 
adjusted  by  a  perforated  cork. 

When  the  boiling-points  of  different  liquids  are  nearly  equal, 
the  density  of  one  of  them  may  sometimes  be  increased  by  the 
addition  of  some  soluble  matter,  which,  if  both  liquids  are  to  be 
saved,  can  afterwards  be  readily  removed. 

Too  sudden  ebullition  must,  in  all  cases,  be  avoided,  and  the 
fire  should  be  gradually  increased,  whether  the  heating  vessel  be 
of  glass  or  metal.  The  only  exceptions  to  this  rule  occur  in  the 
use  of  water  or  saline  baths. 

DISTILLATION  OF  LIQUIDS.— The  STILL  is  the  most  convenient 


336 


DISTILLATION    OF    LIQUIDS. 


implement  for  the  distillation  of  large  quantities  of  material. 
Retorts  are  more  applicable  to  nicer  operations. 

The  arrangement  of  a  retort  for  the  process  of  distillation  is 
very  analogous  to  that  of  a  still.  The  body  is  the  recipient  of 
matter  to  be  heated,  and  is  the  portion  to* which  heat  is  applied ; 
the  beak  is  the  condenser,  and  the  glass  receiver,  the  recipient  of 
the  distillate.  The  exit  nozzle  fitting  upon  the  end  of  the  worm 
and  leading  into  the  recipient,  should  never  project  so  far  as  to 
dip  into  the  distillate.  If  a  globular  receiver  is  not  at  hand,  an 
ordinary  glass  bottle  for  retort  distillations,  or  a  carboy  for  those 
in  the  still,  are  excellent  substitutes,  as  it  is  very  easy  to  make 
the  connection  by  using  a  curved  adapter,  Fig.  249,  and  adjust- 
ing it  to  the  mouth  of  the  receiver,  as  in  all  other  cases,  through 
a  perforated  cork. 

Sometimes  the  receivers  themselves  are  drawn  out  at  the  neck 
into  a  tube  which  enters  a  flask,  as  at  Fig.  260,  or  else  the  tubu- 
lure  is  fitted  with  a  perforated  cork  for  the  passage  of  a  tube, 
which  answers  as  well  the  purpose  of  a  conduit.  The  flask 


Fig.  261. 


Fig.  262. 


which  receives  this  tube  is  also  fitted  with  a  perforated  cork, 
through  which  passes  another  tube  c,  Fig.  261,  for  the  escape  of 
uncondensed  vapors. 

The  refrigeration  of  the  receiver  is  readily  accomplished  by 
either  of  the  arrangements  shown  at  Figs.  247,  248,  250. 

The  uncondensed  gases  are  allowed  exit  through  a  small  glass 
tube,  adapted  to  the  tubulure  in  the  top  of  the  receiver,  and  lead- 
ing upwards  under  a  hood,  or  else  downwards  into  a  bottle  of 
some  fluid,  which  absorbs  them,  and  thus  prevents  the  contami- 
nation of  the  atmosphere. 


DISTILLATION  OF  LIQUIDS.  337 

It  is  of  great  importance  that  the  vessels  in  use  for  distillation 
should  always  be  free  from  foreign  substances ;  and  both  the  re- 
tort, still,  adapter,  and  worm,  immediately  after  each  process, 
should  be  cleansed  by  repeated  rinsings  with  water,  so  that  they 
may  be  clean  and  ready  for  the  next  operation. 

As  the  ebullition  of  certain  liquids  is  attended  with  foaming 
and  spirting,  it  is  necessary  to  break  the  force  of  these  sudden 
eruptions  of  vapor,  by  some  mechanical  means.  This  can  be 
effected  often  by  the  addition  of  platinum  scraps  to  corrosive 
liquids,  and  of  fragments  of  glass  to  those  which  boil  at  low  tem- 
peratures and  are  without  action  upon  that  substance.  This  pre- 
caution prevents  damage  to  the  vessel,  and  allows  the  boiling  to 
proceed  tranquilly.  The  use  of  the  water  bath  obviates  the 
necessity  of  this  preventive,  and  is  almost  indispensable  in  the 
distillation  of  liquids  holding  in  solution  certain  vegetable  princi- 
ples, which  are  sensitive  to  the  decomposing  influence  of  heat. 

In  distilling  oil  of  vitriol  in  a  glass  retort,  the  deposition  of 
sulphate  of  lead  endangers  the  safety  of 
the  retort,  and  the  purity  of  the  distillate,  Fig'  263' 

by  an  explosive  ebullition.  To  avoid  this 
difficulty,  Berzelius  sets  the  retort  one- 
third  into  the  truncated  cone  of  sheet 
iron,  Fig.  263,  strews  sand  around  the 
edge  of  the  cone,  surrounds  it  with  brick, 
and  hangs  a  flat  cone  of  sheet  iron  about 

a  half  inch  above  the  retort.  The  retort  is  half  filled  with  acid, 
and  coals  placed  on  the  cone  inside  the  bricks.  Another  method 
of  Berzelius  is  to  precipitate  the  lead  salt  by  dilution  with  water, 
to  concentrate  the  acid  in  a  platinum  capsule,  and,  finally,  to 
distil  in  a  dome-topped  furnace,  a  quiet  distillation  being  pro- 
moted by  the  introduction  of  platinum  wire  into  the  retort. 

If  the  retort  is  tubulated,  there  is  no  difficulty  in  charging  it 
neatly,  because  its  contents  can  be  added,  without  danger  of 
spilling,  through  a  wide-barrelled  funnel ;  but  when  plain,  it  is 
necessary,  in  order  to  prevent  the  adherence  of  particles  to  the 
sides  of  the  beak,  to  stand  it  on  end,  as  shown  in  Fig.  264,  and  to 
fill  it  through  the  neck  by  means  of  a  straight  funnel-tube  with 
its  barrel  reaching  to  the  bottom. 

The  matters,  if  solid,  should  always  be  bruised  or  triturated  to 

22 


338 


DISTILLATION    OF   LIQUIDS. 


Fig.  264. 


powder  and  added  portionwise.     In  this  way  the  neck  of  the 
retort  is  kept  clean. 

The  joints  of  retorts  and  glass  distillatory  vessels  may  be  luted 
with  strips  of  muslin  soaked  in  a  solution  of  bone 
glue.  Those  of  metallic  vessels,  with  a  dough 
of  whiting  and  flaxseed  meal,  which,  when  dry, 
may  be  rendered  still  more  impermeable,  by  a 
covering  of  muslin,  prepared  as  above,  with  bone 
glue.  When  one  vessel  is  adapted  to  the  other 
by  means  of  perforated  corks,  these  latter  should 
be  payed  over  with  wax  or  more  economically 
with  the  flaxseed  or  whiting  dough.  If  the  dis- 
tillate decomposes  organic  matter,  the  use  of 
corks,  flaxseed,  and  similar  means,  must  be 
avoided,  and  the  joints  made  tight  by  using  ap- 
paratus, the  connecting  parts  of  which  are  nicely 
adapted  to  each  other  by  ground  joints. 

All   matters  which   readily  generate  very  volatile   products 
should  be  distilled  over  BATHS,  of  which  those  made  of  liquids 
are  to  be  preferred.     It  is  very  easy  to  arrange 
the  retort  in  a  suitable  vessel,  by  resting  it  upon 
a  braided  straw  ring,  Fig.  265,  and  steadying 
its  neck  in  a  clamp  support.     The  beak  of  the 
retort  should  also  be  elongated  by  attaching  it 
to  a  Liebig  condenser,  Fig.  267,  so  as  to  extend  the  cooling  sur- 
face.    If  the  distillate  is  readily  condensable,  the  receiver  may 

Fig.  266. 


Fig.  265. 


be  kept  sufficiently  cold  by  a  bath  of  cold  water,  as  shown  in 
Figs.  250,  266 ;   otherwise  the  use  of  FRIGORIFIC   MIXTURES 


DISTILLATION   OF  LIQUIDS. 


339 


becomes  necessary.  The  mixture  should  entirely  surround  the 
recipient,  and  as  it  becomes  warm  or  liquefies,  new  portions  must 
be  added.  If  ice  or  other  solid  is  used,  the  syphon  in  position, 
as  shown  at  6,  Fig.  266,  will  keep  the  pail  constantly  free  from 
the  liquefied  excess. 

The  proper  arrangement  of  an  apparatus  with  Liebig's  con- 
denser, is  shown  in  Fig.  267. 

Fig.  267. 


In  the  distillation,  particularly  of  essences  and  oils,  the  mate- 
rial, if  it  is  ligneous,  must  be  soaked,  previous  to  its  transfer  to 
the  still,  in  which  it  should  be  made  to  rest  upon  a  cullendered 
diaphragm,  Figs.  22,  27,  to  prevent  contact  with  the  heated 
bottom  of  the  vessel.  A  proper  vehicle  is  then  added,  and  the 
operation  continued  by  the  application  of  heat.  The  water,  or 
other  liquid,  and  volatile  matter  are  vaporized,  and  the  two  be- 
coming involved  pass  over  together.  When  these  two  products 
differ  in  density,  as  is  commonly  the  case,  a  very  convenient 
means  of  separating  them  as  they  pass 
over,  is  afforded  by  the  Florentine  re- 
ceiver, shown  in  Fig.  268.  A  is  the 
body  of  the  recipient,  and  D  its  mouth 
through  which  the  distillate  enters. 
The  tubulure  B  is  for  the  reception  of 
the  beak  (a  curved  glass  tube),  c.  As 
soon  as  the  condensed  distillate  reaches 
the  receiver,  the  lighter  body  rises  to  the  top,  and  there  retains 
its  position,  and  when  the  contained  amount  of  the  two  fluids 


Fig.  268. 


340 


DISTILLATION   OF  GASES. 


Fig.  269. 


reaches  the  level  of  the  mouth  of  the  beak,  the  one  which  is  most 
dense  runs  off.  The  level  being  kept  thus  constant,  the  lower 
stratum  of  fluid  is  separated  from  the  upper  as  fast  as  any  distil- 
late comes  over,  leaving  the  lighter  liquid  to  be  emptied  from  the 
receiver  after  the  completion  of  the  process. 

If  the  heavier  product  is  the  object  of  the  distillation,  as  is 
sometimes  the  case,  then  the  form  of  the  reci- 
pient may  be  with  advantage  varied,  as  shown 
in  Fig.  269.  The  stop-cock  in  the  barrel 
allows  its  separation  and  discharge  from  the 
lighter  body  as  soon  as  a  sufficient  quantity 
has  subsided. 

When  volatile  oils  and  some  other  bodies 
are  obtained  by  the  above  process,  the  water 
which  is  generally  employed  as  the  vehicle, 
and  which  is  separated  as  we  have  described, 
should  be  reserved,  for  being  already  more  or 
less  charged  with  volatile  matter,  it  may  be 
economically  used  in  redistilling  the  same 
material,  in  case  it  should  yield  its  product 
reluctantly.  This  repeated  distillation  of  the 
.  distillate  over  the  same  material  is  termed 

Cohobation,  and  is  resorted  to  necessarily,  in  many  instances,  that 
the  material  may  be  entirely  exhausted  of  its  volatile  matter. 

Rectification  is  the  redistillation  of  the  distillate,  either  alone 
or  with  some  absorbent  material  to  free  it  from  water,  acid,  or 
other  impurity. 

DISTILLATION  OF  GASES.  —  The  term  distillation  cannot,  in 
all  instances,  be  applied  with  entire  precision  to  the  processes 
concerned  in  the  manufacture  of  gases.  But,  as  gaseous  bodies, 
when  intended  to  be  retained,  are  usually  prepared  by  modes  pre- 
cisely similar  to  those  employed  in  liquid  distillation,  it  has  been 
thought  proper  to  introduce  their  consideration  in  this  place. 

The  generation  and  distillation  of  gases  are  generally  made 
simultaneous  operations.  As  their  elasticity  is  such  as  to  prevent 
condensation  by  ordinary  means,  they  are  either  collected  in 
solution  with  water,  or  other  fluid,  or  in  their  gaseous  state  in 
gasometers.  The  arrangement  of  the  required  apparatus,  though 


DISTILLATION   OP   GASES. 


341 


bearing  analogy  to  that  for  ordinary  distillations,  differs  in  many 
little  but  material  points. 

If  the  gas  is  readily  evolved  without  the  aid  of  heat,  as  in  the 
case  of  hydrogen,  carbonic  acid,  sulphuretted  hydrogen,  &c.,  the 
generator  may  be  a  simple  flask  A,  Fig.  270.  This  flask  is  the 

Fig.  270. 


recipient  of  the  material  from  which  the  gas  is  to  be  eliminated. 
The  funnel-tube  B,  reaching  nearly  to  its  bottom,  is  the  inlet  of 
the  acid,  or  other  reagent,  by  which  the  action  is  to  be  produced, 
and  the  bent  tube  c  is  for  the  exit  of  the  disengaged  gas.  An 
ordinary  wide-mouth  green  glass  bottle  will  answer  the  purpose 
excellently  in  most  cases,  as  exhibited  in  Fig.  271,  which  shows 
an  apparatus  of  this  kind  for  passing  gas  through  liquids,  when 
its  absorption  is  required, — as  in  the  precipitation  of  solutions  in 
analysis.  When  the  generator  is  to  be  connected  with  a  com- 
bustion or  DESICCATION  tube,  as  at  Fig.  218,  the  bent  tube  can  be 
removed.  In  this  instance,  and,  indeed,  with  better  results  in  all 
cases,  the  angular  tube  should  be  blown  with  a  bulb  in  its  centre 
for  the  reception  of  a  plug  of  raw  cotton,  which  intercepts  the 
passage  of  liquid,  and  solid  particles  of  foreign  matters. 

The  exit  tube  is  frequently  divided  into  two  pieces,  and  con- 
nected together  by  a  piece  of  india-rubber  tubing,  as  shown  by 
Fig.  271.    A  flexible  joint,  B,  is  thus  formed,  and  affords  the  con- 
venience of  giving  the  tube  any  required  direction. 
"    When,  in  particular  instances,  it  is  inexpedient  to  use  the 


342 


DISTILLATION   OF   GASES. 


funnel-tube,  the  generating  bottle  or  flask  may  have  the  form 
presented  by  Fig.  272,  which  shows  the  exit  tube  issuing  from  a 
tubulure  in  one  entire  length,  with  two  angular  bends. 


Fig.  271. 


Fig.  272. 


For  certain  operations,  the  bottle  and  delivery-tube  are  in  one 
piece, — the  part  A,  or  mouth,  forming  the  funnel  tube ;  B  the 
flask  portion  or  generating  chamber ;  and  c  the  exit  tube.  This 


Fig.  273. 


Fig.  274. 


arrangement  is  adapted  to  experiments  with  corrosive  gases, 
which  act  upon  artificial  joints  and  loosen  them.  When  made  of 
diminutive  size,  and  with  a  long  exit  tube,  as  shown  by  Figs.  274, 
275,  they  are  very  convenient  for  small  experiments  and  testing, 
such  as  passing  gas  into  test-tubes  and  the  like. 

The  usual  form  of  funnel-tubes  is  as  shown  by  B,  Fig.  270,  which 
consists  of  a  straight  tube  surmounted  by  a  funnel.     This  funnel 


DISTILLATION   OF   GASES. 


£43 


Fig.  276. 


is  sometimes  made  as  at  Fig.  299.  To  save  the  necessity  of 
boring  separate  holes  in  the  cork  for  the  funnel  and  the  exit  or 
delivery-tube,  Vogel  combines  the  two  in  one  piece,  as  seen  at 
Fig.  276.  The  main  stem  is  an  ordinary  funnel-tube  e  d,  to 
which  is  joined  a  short  piece  of  wider  tube  a  5,  with 
a  lateral  branch  f  g  o.  The  tube  a  b  being  fitted 
to  the  cork  of  the  generating  flask,  so  that,  when 
in  place,  it  may  reach  the  bottom  of  that  vessel,  is 
then  ready  to  receive  the  acid  through  the  funnel. 
The  gas  disengaged  flows  out  through  a  b  and  its 
continuation  f  g  o,  thence  it  may  be  led  into  any 
course  by  a  tube  connecting  with  o,  by  a  flexible 
india-rubber  attachment. 

The  perforations  in  the  cork  must  be  only  large 
enough  for  the  transit  of  the  tubes,  and  the  joints 
must  be  perfectly  tight.  To  render  the  cork  itself 
impermeable,  sealing-wax  should  cover  both  of  its 
surfaces.  This  arrangement  of  the  tubes  obviates 
all  liability  of  explosion.  If  condensation  takes 
place  in  the  interior  of  the  generating  vessel,  the 
resistance  from  the  funnel-tube  being  more  feeble  than  tjiat  op- 
posed by  the  water  of  the  trough  or  receiving  vessel,  the  air 
enters.  So  also,  if  from  any  cause  the  passage  of  the  gas  through 
the  exit  tube  should  be  obstructed,  its  pressure  upon  the  liquid 
in  the  generator  forces  it  upwards  through  the  funnel-tube,  so 
that  it  may  escape  instead  of  being  allowed  to  accumulate  until 
explosion  takes  place. 

When  it  is  desirable  to  have  the  gas  free  from  impurity,  an 
indispensable  consideration  if  it  is  to  be  used  in  analyses,  it 
should,  previous  to  its  entrance,  be  passed 
through  a  small  quantity  of  water,  or 
other  fluid,  which  will  dissolve  out  or 
chemically  attract  such  foreign  matter  as 
might  have  an  injurious  effect  upon  the 
liquid  to  be  acted  upon.  A  suitable  ar- 
rangement for  such  purposes,  and  one 
well  adapted  to  the  generation  of  sulphu- 
retted hydrogen  gas,  is  shown  in  Fig. 
277 ;  A  is  the  bottle  containing  the  proto- 


Fig.  277. 


344 


DISTILLATION   OF   GASES. 


sulphuret  of  iron,  water,  and  sulphuric  acid,  and  provided  with 
funnel  and  disengagement-tubes  as  usual,  the  latter  plunging  in 
the  water  of  a  smaller  bottle  B,  from  which  a  disengagement-tube 
D,  nearly  as  high  as  that  of  the  bottle  A,  issues,  so  as  to  lead  the  gas 
disengaged  into  a  beaker  or  other  vessel  containing  the  liquor  to 
be  operated  upon ;  but  the  first  disengagement-tube  c  is  in  two 
pieces,  united  by  india-rubber,  and  the  bottles  A,  B,  are  connected 
together  by  a  strong  band  of  sulphurized  india-rubber  j  or  of  gutta- 
percha  G,  so  that  the  two  bottles  may  be  lifted  at  once  as  if  they 
were  in  one,  wedges  of  cork  E  E  being  forced  between  the  two 

Fig.  278. 


bottles,  so  as  to  keep  the  strip  of  india-rubber  G  and  the  tube  c 
properly  adjusted.  Fig.  278  exhibits  the  apparatus  with  stiff 
tubes,  and  a  short  vial,  as  the  intermediate  vessel. 


Fig.  279. 


When  heat  is  required  to  cause  or  to  promote  the  elimination 
of  a  gas,  the  generating  vessels  may  be  either  tubes,  flasks,  or 
retorts. 

The  facility  with  which  glass  tubes  may  be  fashioned  over  the 


TEST-TUBE. 


345 


blowpipe  flame  into  any  desired  shape,  renders  them  particu- 
larly applicable  to  small  operations.  Fig.  279  exhibits  a  tube- 
apparatus  for  the  distillation  of  hydrobromic  acid.  It  consists  of 
a  glass  tube  A  B,  to  which  is  adapted  a  disengagement-tube  con- 
veying the  gas  under  the  bell  c,  filled  with  mercury.  The  bromine 
is  placed  at  A,  and  at  B  are  small  particles  of  moist  phosphorus 
intermixed  with  bruised  glass.  Gentle  heat  being  applied  at  A, 
the  vaporized  bromine  reacts  upon  the  phosphorus  and  water, 
producing  phosphorous  acid,  and  disengaging  hydrobromic  acid 
gas,  which  passes  over  into  the  bell-receiver  and  displaces  the 
mercury. 

A  test-tube,  Fig.  280,  fitted  with  a  bent  tube,  serves  very  con- 
Fig.  280. 


Fig.  281. 


veniently  for  generating  small  quantities  of  gas  for  analytic  or 
even  experimental  purposes.  Any  other  forms  that  may  be 
needed  will  be  suggested  by  the  requirements  of  the  process  or 
the  ingenuity  of  the  operator,  and  can  readily  be  fashioned  after 
the  instructions  given  upon  GLASSBLOWING. 

Another  very  convenient  form  of  tube  generator  is  that  known 
as  Marsh's  Arsenic  Apparatus,  Fig.  281.  It  consists 
of  an  elbowed  tube  of  Bohemian  glass,  fitted  with  a 
stop-cock  and  jet,  the  whole  to  be  supported  by  a 
suitable  stand  or  pedestal.  The  length  of  the  tube 
may  be  sixteen  inches,  and  its  width  three-fourths  of 
an  inch. 

The  elbow  being  charged  with  some  pieces  of  puri- 
fied zinc,  the  liquid  containing  the  suspected  com- 
pound is  acidulated  with  oil  of  vitriol,  and  poured 
into  the  long  leg.  The  arsenical  combination  becomes  decom- 
posed by  the  nascent  hydrogen  generated  by  the  action  of  the 
sulphuric  acid  upon  the  zinc  and  water,  and  makes  its  exit  through 


34(5 


FLORENCE  FLASK. 


Fig.  282. 


the  cock  at  the  short  arm,  as  arseniuretted  hydrogen,  which  may 
be  recognized,  when  ignited,  by  its  bluish-white  flame,  and  the 
appearance  of  the  deposit  upon  a  porcelain  plate  held  over  it. 
The  stop-cock  allows  the  facility  of  regulating  or  stopping  off  the 
supply  of  gas  when  required. 

Next  to  the  tubes,  a  Florence  flask  is  the  most  economical 

vessel  for  conducting  small  opera- 
tions. Fig.  282  exhibits  one  under- 
going the  process  of  being  heated  by 
a  small  spirit-lamp.  The  tripod 
upon  which  the  flask  rests,  is  sur- 
rounded by  a  tin  plate  screen  of  a 
foot  in  height,  to  confine  the  heat  of 
the  lamp.  The  exit  tube  conveys 
the  gas  into  the  beaker  glass  c, 
which  contains  the  solution  to  be 
saturated.  Flasks  of  very  thin  glass, 
and  made  uniform  throughout,  are 
blown  expressly  for  this  purpose.  The  exit  tube  is  bent  so 
that  it  may  be  used  with  bell  glasses  over  a  pneumatic  trough,  as 
in  Fig.  279. 

Retorts  are  only  convenient  when  large  quantities  of  material 
are  to  be  operated  upon.     For  those  processes  which  require  high 
furnace  temperatures  a  metallic  retort  is  needed.     Fig.  282  ex- 
Fig.  283. 


hibits  one  of  iron,  and  another  form  has  already  been  presented 
at  Fig.  256.     It  is  fitted  with  a  very  convenient  coupling  or 


KEMP'S   GENERATING  JAR. 


347 


•gallows  screw,  by  which  the  neck  may  be  connected  with  flexible 
lead  or  other  exit  pipes.  The  accompanying  circular  plate,  in 
two  pieces,  serves  both  as  a  cover  to  the  furnace  and  as  a  support 
for  the  neck  of  the  retort  to  retain  it  in  place. 

The  requirements  of  the  laboratory  are  such,  in  respect  to  sul- 
phuretted hydrogen  and  pure  hydrogen  gases,  as  to  render  neces- 
sary some  convenient  means  for  obtaining  a  constant  supply  of 
them,  at  any  and  all  times,  without  the  trouble  and  delay  of  ar- 
ranging an  apparatus  in  every  instance.  To  this  end  several 
apparatus  have  been  contrived,  and  we  have  already  described 
one  at  p.  343.  Another,  known  as  Kemp's  Generating  Jar,  is 
shown  by  Fig.  284.  It  consists,  simply,  of  a  tall  glass  jar  A, 

Fig.  284. 


with  a  lateral  tubulure  near  the  top.  Surmounting  the  top  is  a 
glass  plate  cover,  bored  in  the  centre,  and  ground  on  the  under 
surface  so  as  to  form  a  close  joint  with  the  ledge  of  the  jar. 
Through  the  centre  hole  passes  a  copper  wire,  to  the  end  of 
which  is  suspended  an  earthenware  basin  or  basket  D.  This 
wire  is  held  in  position  by  a  cork  tightly  adjusted  in  the  centre 
hole.  The  basket  is  the  recipient  of  the  zinc,  sulphuret  of  iron, 
or  other  solid  matter,  to  be  used  for  generating  the  gas.  E  is  a 
tube  fitted  to  the  lateral  tubulure,  and  containing  water  for  wash- 
ing the  gas  in  its  transit  to  the  delivery-tube  F.  This  latter  is 
connected  with  the  former  by  means  of  a  flexible  caoutchouc  tube. 


348 


HYDROGEN   GAS   APPARATUS. 


The  jar  is  kept  filled  with  acid  liquor  to  the  height  shown  by  the 
shaded  part  of  the  drawing,  and  when  gas  is  needed,  the  cullen- 
dered  basin  D  is  to  be  pushed  down  into  the  acid  by  depressing 
the  wire  c,  and  kept  immersed  as  long  as  a  flow  of  gas  is  required. 
The  evolution  of  gas  may  be  discontinued  at  will,  merely  by 
raising  the  wire  so  as  to  draw  the  basin  out  of  the  liquor.  If  a 
rapid  generation  of  gas  is  desired,  it  may  be  fully  immersed  below 
the  surface,  but  not  too  deeply,  for  the  acid  liquor  is  weaker  in 
the  lower  strata,  after  it  has  acted  sufficiently  long  on  the  solid 
to  convert  a  portion  of  it  into  a  dense  solution.  A  partial  im- 
mersion, on  the  other  hand,  produces  a  gentle  evolution  of  gas. 
Another  apparatus,  for  the  same  purpose  as  the  foregoing,  but 
on  a  more  extended  scale,  is  that  recently  devised  by  Fresenius, 
for  disengaging  sulphuretted  hydrogen  gas,  and  illustrated  by  the 
accompanying  drawing.  It  is  always  ready  for  use,  at  a  great 

Fig.  285. 


saving  of  material,  and  yet  yields,  from  a  single  charge,  a  supply 
of  gas  sufficient  for  a  month's  service,  with  the  least  possible  dis- 
agreeable odor. 

It  consists  of  two  lead  cylinders  # ,  £>,  e,  d,  e,  /,  g,  A,  Fig.  285, 
of  equal  size,  all  their  joints  being  soldered  with  pure  lead.  Their 
diameter  is  12  inches,  and  their  height  13  inches.  Resting  upon 


HYDROGEN  GAS  APPARATUS.  349 

leaden  feet,  about  1J  to  2  inches  above  the  bottom,  is  a  per- 
forated leaden  shelf  i.  An  opening  k,  of  about  three  inches 
diameter,  and  closed  by  a  ground  glass  stopper,  serves  as  the 
entrance  for  the  sulphuret  of  iron  from  which  the  gas  is  to  be 
generated.  The  glass  stopper  is  screwed  down  with  a  greased 
leather  washer  between  the  two  surfaces.  An  opening,  for  run- 
ning off  the  residual  sulphate  of  iron  liquor,  is  shown  at  s. 

"  It  may  be  seen  in  the  section,  A,  that  it  is  placed  at  a 
somewhat  deeper  part  of  the  bottom  g,  h ;  the  diameter  of  this 
opening  is  1^  inches.  It  is  closed  by  means  of  a  thick,  ground, 
leaden  stopper,  pressed  down  upon  its  mouth  by  a  screw.  The 
arrangement  of  the  filling  tube  m  is  sufficiently  evident  from  the 
drawing,  as  is  likewise  that  of  the  tube  d,  h,  which  is  destined  to 
convey  the  acid  from  the  upper  into  the  lower  vessel,  and  from 
this  into  the  former.  It  will  be  noticed  that  it  extends  into  the 
deepened  part  of  the  bottom  $r,  h,  but  does  not  actually  touch. 
The  tube  c,  e,  is  closed  at  the  top,  and,  therefore,  does  not  com- 
municate in  any  way  with  the  upper  vessel.  It  is  intended  to 
convey  off  the  gas  disengaged  in  e,  /,  g,  h,  and  with  that  view  is 
furnished  with  a  lateral  tube  0,  which  can  be  closed  by  the  cock 
n.  The  use  of  the  tube  p  will  be  seen  below.  The  tube  q  is 
closed  at  both  ends,  and  serves  only  as  a  support.  These  tubes 
are  all  of  a  half  inch  internal  diameter,  and  should  not  be  too 
thin  in  substance.  When  the  apparatus  is  to  be  filled  it  is  done 
in  the  following  manner  :  about  seven  and  a  half  pounds  of  melted 
sulphuret  of  iron,  in  small  fragments,  are  introduced  through  the 
opening  &,  so  as  to  rest  upon  the  perforated  shelf  i,  when  k  is 
carefully  closed,  ?,  of  course,  being  likewise  closed. 

The  cock  u  is  then  closed,  and  a,  6,  c,  d,  filled  with  dilute  sul- 
phuric acid,  by  pouring  through  the  funnel  first  one  and  one  half 
gallons  of  water,  and  then  thirty  fluid  ounces  of  concentrated 
sulphuric  acid.  The  air  contained  in  a,  b,  c,  d,  escapes  mean- 
while through  the  tube  jt?,  even  when  it  is  connected  with  the 
bottles  r,  s,  t.  When  now  the  cock  n  is  opened,  as  well  as  one 
of  the  cocks  u,  the  acid  flows  through  the  tube  d,  h,  into  the 
vessel  e,f,  g,  h.  At  first  air  escapes  from  the  tube  o,  and  then 
sulphuretted  hydrogen,  as  soon  as  the  acid  comes  in  contact  with 
the  sulphuret  of  iron ;  after  a  time  all  the  air  is  driven  out.  As 
seen  in  B,  the  tube  o  is  bent  and  carried  along  horizontally. 


350  COLLECTION   OF   GASES. 

To  it  are  attached  as  many  ordinary  brass  cocks  M,  u,  as  may  be 
desired.  They  are  connected  with  washing  bottles  in  the  manner 
represented,  by  means  of  a  piece  of  vulcanized  caoutchouc  tube. 
When  the  cock  u  is  opened,  as  well  as  the  cock  n,  a  stream  of 
gas,  of  any  desired  amount,  is  obtained,  which  continues  per- 
fectly uniform  for  days.  When  the  cocks  w,  U,  are  closed,  the 
gas  disengaged  in  e,  /,  g,  A,  presses  the  acid  upwards  through 
the  tube  A,  d ;  and  when  the  sulphuret  of  iron  is  no  longer  im- 
mersed in  the  acid  the  action  ceases.  This,  however,  does  not 
take  place  instantaneously,  for  there  is  always  some  acid  left 
adhering  to  the  sulphuret,  and  small  fragments  of  the  latter  fall 
through  the  holes  of  the  shelf,  and  maintain  the  action  for  a 
certain  time.  Since  the  gas  can  no  longer  escape  through  0,  it 
presses  the  liquid  in  b  d  upwards,  bubbles  up  through  the  acid 
contained  in  fl,  b,  <?,  d,  and  escapes  through  p.  In  order  to  pre- 
vent this  gas  from  being  lost  and  contaminating  the  air,  the 
bottles  r,  s,  £,  are  attached ;  r  contains  cotton-wool,  which  sup- 
plies the  place  of  water  in  an  ordinary  washing  bottle,  as  water 
would  readily  run  back  into  the  apparatus ;  s  and  t  are  charged 
with  solution  of  ammonia  in  such  quantity  as  to  be  entirely  con- 
tained by  either  bottle ;  for  as  the  stream  of  gas  is  here  inter- 
mittent, the  liquid  may  be  forced  backwards  and  forwards  from 
one  bottle  to  the  other.  A  constant  supply  of  sulphuret  of  am- 
monia is  thus  obtained  as  a  by-product.  When  at  last  the  disen- 
gagement of  gas  ceases,  the  acid  has  been  all  consumed,  but  not 
the  sulphuret,  which  is  equivalent  to  double  the  above  quantity 
of  acid.  It  is  therefore  necessary  to  run  off  the  solution  of  sul- 
phate of  iron.  This  is  done  in  the  following  manner : — All  the 
cocks  u  are  closed,  n  left  open,  and  a  dish  placed  under  Z,  which 
is  opened,  and  then  one  of  the  cocks  u  opened.  As  soon  as  the 
air  enters,  the  liquid  runs  off  rapidly,  and  when  it  is  all  removed, 
the  edges  of  the  opening  I  are  washed  with  water ;  it  is  again 
closed,  and  another  quantity  of  acid  added  as  before.  It  is  not 
advisable  to  use  stronger  acid,  for  in  that  case  the  sulphate  of 
iron  would  crystallize.  The  brass  cocks  do  not  suffer  at  all  from 
the  sulphuretted  hydrogen,  and  the  apparatus  answers  all  reason- 
able expectations." 

Collection  of  G-ases. — Gases  are  either  collected  in  the  aeri- 
form state  or  else  in  solution.    When  generated  extemporaneously, 


COLLECTION   OF   OASES.  351 

merely  as  precipitants  of  some  solution,  they  are  passed  through 
the  liquid  contained  in  a  beaker  glass,  as  at  Fig.  282,  and  Fig. 
277,  a  tightly  stretched  paper  cover  being  in  general  all  that  is 
required  to  confine  the  unabsorbed  excess  in  the  vessel. 

If  a  liquid,  as  well  as  a  gaseous  product,  is  generated  simul- 
taneously, then  the  arrangement  of  the  apparatus  may  be  as 
shown  in  Fig.  286.  The  use  of  this  may  be  well  illustrated  by  a 

Fig.  286. 


reference  to  the  manufacture  of  nitrous  oxide  gas.  The  nitrate 
of  ammonia,  the  material  from  which  it  is  generated,  is  placed  in 
the  retort,  the  beak  of  which  is  adjusted  by  means  of  a  perforated 
cork,  to  the  tubulure  of  a  globular  receiver  A.  This  receiver  in  its 
turn  is  connected  by  bent  glass  tubes,  rendered  flexible  by  a 
caoutchouc  joint,  with  a  Wolffe's  bottle  B.  The  latter,  deriving 
its  name  from  that  of  the  inventor,  consists  of  a  bottle,  the  size 
of  which  may  vary  with  the  extent  of  the  operation,  having  in 
this  instance  three  tubulures,  each  of  which  is  fitted  with  a  per- 
forated cork  for  the  passage  of  glass  tubes.  The  first  tube  0, 
Fig.  286,  conducts  the  gas  from  the  receiver,  and  the  central  tube 
acts  as  a  safety  valve.  The  gas  cannot  escape  through  it,  but 
should  condensation  ensue  within  the  bottle,  the  external  air 
rushes  in  and  prevents  the  liquid  from  running  over  into  the 
recipient  or  next  bottle,  if  there  are  two  connected,  by  reason  of 
absorption.  The  third  tube  d  is  the  exit  tube  for  conveying  the 
gas  directly  into  the  recipient,  which  in  this  case  is  a  caoutchouc 
bag  e. 

The  retort,  receiver,  and  Wolffe's  bottle  having  been  connected 


352  COLLECTION   OF   GASES. 

together,  and  the  joints  hermetically  closed,  heat  is  then  gradu- 
ally applied  by  means  of  the  spirit  Argand  lamp.  The  eliminated 
gas  passes  over  into  the  receiver,  there  deposits  the  aqueous 
vapor  with  which  it  is  involved,  and  continues  on  to  the  Wolffe's 
bottle  containing  water,  in  its  transit  through  which  it  parts  with 
the  rest  of  its  aqueous  vapor,  and  its  other  impurities,  and  ulti- 
mately reaches  the  exit  tube  d.  If  the  gas  is  to  be  received  into 
caoutchouc  bags,  Figs.  171,  286,  and  pages  252,  351,  for  inha- 
lation or  other  purposes,  the  connection  may  be  made  directly, 
as  seen  in  the  figure,  by  means  of  a  gallows  screw,  which  allows 
an  empty  bag  to  replace  another,  as  may  be  necessary.  If  the 
bags  are  intended  as  reservoirs  for  the  preservation  of  the  gas, 
their  necks  are  fitted  with  gallows  screw  stop-cocks  and  connect- 
ing nipples. 

If  the  gas  is  to  be  conducted  into  a  Pepy's  gasometer,  as  at 
Fig.  301,  or  under  a  bell-glass  over  a  pneumatic  trough,  as  at 
Fig.  294,  then  instead  of  the  stop-cock  there  must  be  a  flexible 
bent  tube,  of  shape  similar  to  that  attached  to  the  Fig.  271, 
adapted  to  the  third  tubulure  of  the  bottles. 

Lead  pipe  of  a  small  bore  may  be  used  as  a  conduit  when  the 
generated  gas  is  not  corrosive,  but  india-rubber  tube  is  prefer- 
able. The  gallows  screw  then  becomes  the  proper  mode  of  con- 
nection. 

To  favor  the  condensation  of  the  aqueous  impurity  of  the  gas, 
the  globular  receiver  should  be  kept  cool  during  the  distillation. 
'So  also  the  Wolfie's  bottle  must  be  surrounded  by  water,  or  a 
cooling  mixture,  when  the  gas  is  very  volatile,  otherwise  the 
elevation  of  temperature,  which  generally  occurs,  may  cause  its 
dissipation. 

When  two  or  more  gases  are  generated  simultaneously,  they 
may  be  separated  by  the  presence  in  the  receiver  of  an  appropri- 
ate liquid,  which  is  a  solvent  of  one,  but  not  of  the  other  of  them. 
Thus  oxygen  may  be  freed  from  carbonic  acid  by  passing  the 
mixture  through  a  solution  of  caustic  potassa,  which  absorbing 
the  acid  becomes  carbonated,  and  allows  the  transit  of  the  puri- 
fied oxygen.  This  mode  is  adapted  for  this  and  other  purposes 
in  organic  analysis,  the  requisite  apparatus  being  a  five-bulbed 
white  glass  receiver  of  the  form  shown  by  Figs.  287,  288.  Its  ar- 
rangement for  the  purpose  is  given  in  Fig.  139,  a  being  the  com- 


COLLECTION   OF   GASES.  353 

bustion-tube,  in  which  the  substance  to  be  analyzed  is  introduced 
after  its  mixture  with  oxide  of  copper  or  chromate  of  lead,  from 

Fi*-287-  Fig.  288. 


which  it  obtains  the  oxygen  necessary  for  its  combustion.     The 
figure  represents  the  tube  in  its  position,  during  the  analysis,  in 
the  trough-shaped  furnace  of  sheet-iron,  in  which  it  is  heated  by 
being  surrounded  with  ignited  charcoal.     By  means  of  a  per- 
forated cork,  the  combustion-tube  is  connected  with  the  tube  in 
which  the  water  produced  by  the  combustion  is  condensed.     It  is 
filled  with  chloride  of  calcium,  in  order  to  absorb  all  the  vapors 
from  the  carbonic  acid,  which  passes  through  it  into  the  appa- 
ratus m  r  p,  through  which  it  would  be  forced,  were  it  not 
absorbed  by  the  solution  of  caustic  potassa  contained  in  the  lower 
bulbs.     After  the  completion  of  the  combustion,  the  carbonic 
acid  which  remains  in  the  combustion-tube  is  extracted  from  it, 
by  breaking  off  its  pointed  extremity  and  applying  suction  to  the 
other  end  of  the  potassa  apparatus  at  p,  by  which  air  is  drawn 
through  the  whole  apparatus,  and  the  carbonic  acid  absorbed  by 
its  passage  through  the  solution  in  the  potassa  bulbs.    The  weight 
of  the  water  and  the  carbonic  acid,  is  obtained  by  weighing  the 
chloride  of  calcium  tube  and  the  potassa  apparatus  before  and 
after  the  combustion.     For  this  purpose,  each  may  be  conve- 
niently suspended  to   the  supplementary  pan,  Fig.  76,  of  the 
analytic  balance,  p.  112. 

Another  form  of  receiver,  for  similar  operations  to  the  pre- 
ceding, is  shown  by  the  annexed  drawing. 

23 


354 


GENERATION  AND  ABSORPTION   OF   GASES. 


These  two  operations  illustrate  the  generation  of  gases  by 
destructive  distillation ;  but  the  receivers  which  are  used  in  them, 
are  equally  applicable  for  the  collection  of  gases  generated  in 

Fig.  289. 


the  cold ;  the  object  of  the  bulbs  being  to  present  a  larger  extent 
of  liquid  surface  to  the  gas.  Fig.  288  illustrates  the  manner  in 
which  these  bulb-receivers  may  be  filled  with  absorbent  liquor 
without  inconvenience  to  the  operator.  The  lower  end  being 
placed  in  the  liquid,  and  the  upper  connected  by  a  cork  to  a  bent 
tube,  suction  is  then  applied  to  the  latter  by  the  mouth  until  suf- 
ficient liquid  is  drawn  in,  after  which  the  suction-tube  is  discon- 
nected. 

In  the  instance  we  have  been  referring  to,  the  Wolffe's  bottle 
is  used  for  the  purpose  of  retaining  watery  vapor  or  other  impu- 
rities in  its  contained  fluid.  Its  most  common  employment, 
however,  is  when  the  gas  itself  is  intended  to  be  preserved  in 
solution  in  water  or  other  fluid.  For  this  purpose,  the  number 
of  Wolffe's  bottles  is  often  increased  to  three  or  more,  which  are 
connected  together  by  tubes  with  flexible  joints.  In  this  manner, 
any  gas  that  has  remained  unabsorbed  by  the  liquid  in  the  first 
bottle,  is  successively  exposed  to  the  dissolving  influence  of  that 
in  the  others,  until  it  becomes  entirely  liquefied.  The  Wolffe's 
bottles,  the  form  of  which  is  sufficiently  explained  by  the  drawing, 
may,  in  many  cases,  be  well  replaced  by  wide-mouthed  jars  or 
bottles,  with  two  or  three  perforations  in  their  corks,  and  which 
may  be  made  to  answer  all  the  purposes  of  the  more  expensive 
apparatus. 


GENERATION  AND  ABSORPTION   OF  GASES.  355 

Fig.  290  represents  an  apparatus  for  the  generation  and  ab- 
sorption of  gas ;  a  being  the  heating  vessel,  the  contents  of  which 


Fig.  290. 


should  fill  only  half  its  capacity,  so  that  they  may  not,  upon  too 
sudden  reaction,  run  over  into  the  recipient;  b  the  recipient,  either 
for  the  condensation  of  aqueous  vapor,  or  the  abstraction  of 
impurity  by  a  contained  liquid,  and  the  three  Wolffe's  bottles, 
half  filled  with  water,  the  receptacles  of  the  eliminated  gas.  As 
the  volume  of  the  liquid  in  the  Wolffe's  bottles  increases  propor- 
tionably  to  the  amount  of  gas  received  and  dissolved,  they  should 
not  be  more  than  half  filled  at  the  commencement.  So  also  the 
intermediate  receiver  should  have  but  a  very  shallow  depth  of 
liquid,  else  it  will  take  up  gas  as  well  as  the  impurities,  and  thus 
cause  a  loss.  The  water  in  the  first  bottle  is  the  first  to  become 
saturated,  and  all  the  gas  which  is  not  absorbed  passes  over  into 
the  second  and  third  bottles,  through  the  delivery-tubes  and  tran- 
sit-tubes 5,  a.  This  arrangement  is  that  usually  adapted  for  the 
distillation  of  acid,  ammoniacal,  and  other  gases,  which  are  con- 
densed by  solution. 

The  tubes  must  be  adjusted  to  the  tubulures  by  corks  (see 
Chap.  XXXI),  in  such  an  exact  manner  as  to  form  an  air-tight 
joint ;  and  the  connections  of  the  glass  tubes  should  be  flexible, 
and  formed  of  india-rubber  tube.  The  tubes  c  passing  down 
through  the  centre  of  the  corks  and  ending  at  d,  just  below  the 


356 


ABSORPTION   OF  GAS. 


level  of  the  liquid  in  the  bottles,  serve  for  admission  of  air,  when 
from  any  cause  the  internal  pressure  may  become  diminished,  and 
are  thus  a  safeguard  against  the  liquid  running  back  by  the  force 
of  external  atmospheric  pressure,  from  the  last  bottle  to  the  third, 
second,  first,  and  even  to  the  flask.  This  diminution  of  external 
pressure  sometimes  proceeds  from  a  prompt  absorption  of  the 
gas,  a  sudden  stoppage  in  the  delivery  of  it,  or  a  depression  of 
the  temperature  in  the  generating  flask. 

When  necessary,  any  other  liquid  may  be  made  to  replace  the 
water  in  the  bottles.  For  example,  aqua  ammonise  when  it  is 
desired  to  make  a  chloride  or  carbonate  of  that  base,  and  lime 
milk  for  the  solution  of  chlorine,  &c.  &c. 

The  inconvenience  and  delay  in  arranging  a  series  of  Wolffe's 
bottles  for  distillation,  from  the  trouble  of  nicely  adjusting  the 
tubes  and  corks  to  the  tubulures,  induced  Letorel  to  suggest 
a  more  expedient  substitute,  which  is  particularly  serviceable  in 
those  operations  which  would  be  destructive  of  the  cork-fittings 
of  the  Wolffe's  apparatus.  The  connections  are  formed  by  water- 
joints,  and  the  apparatus,  comprising  three  glass  cylinders,  is  re- 
presented, in  vertical  sections,  by  the  three  diagrams  following : 


Fig.  291. 


Fig.  292. 


"  The  outer  and  inner  cylinders  A,  B,  have,  severally,  three 
grooves  perpendicular  to  their  base,  and  at  corresponding  points 
of  their  circumference,  but  in  opposite  directions.  The  inter- 
mediate cylinder  c  is  plain,  and  is  inserted  within  A  over  B.  The 
liquid  used  to  shut  off  communication  with  the  exterior  air  is 
placed  in  the  outer  cylinder,  and  the  liquid  to  be  brought  in  con- 


ABSORPTION   OF  GAS. 


357 


tact  with  the  gas  is  placed  in  the  inner  vessel.  The  gas  is  con- 
ducted into  B  by  the  bent  tube  E,  and  the  unabsorbed  portion 
escapes  by  the  tube  F.  Both  these  tubes  fit  in  the  pairs  of  oppo- 
site grooves.  The  third  pair  of  grooves  is  for  a  safety-tube,  Fig. 

Fig.  294. 


293,  if  requisite.  The  mode  of  connecting  a  series  of  these  ves- 
sels will  be  sufficiently  evident  from  the  wood-cut.  This  arrange- 
ment may  likewise  be  employed  for  generating  gases,  as  shown  in 


Fig.  295. 


Figs   294  and  295.     The  liquid  used  for  the  hydraulic  joint  must 
be  adapted  to  the  nature  of  the  operation.     In  the  preparation  of 


358  WOLFFE'S  BOTTLES. 

carbonic  acid  or  the  bicarbonates,  water  will  answer.  For  other 
purposes,  mercury,  solutions  of  chloride  of  calcium,  of  caustic 
alkali,  &c.,  may  be  used.  The  cylinder  c  must  be  loaded  with  a 
sheet  of  lead  in  order  to  keep  it  steady." 

For  micro-distillations,  the  Wolffe's  bottle  may  consist  of  a 
U-shaped  tube,  bent  as  seen  in  Fig.  296.  These  condensers  can  be 
formed  into  a  series  by  means  of  corks  and  bent  tubes,  as  shown 

Fig.  296.  Fig.  297. 


by  Fig.  297.  They  are  very  convenient  for  minute  experiment, 
and  admit  of  the  use  of  either  liquid  or  solids,  as  agents  for  ab- 
sorbing gases.  The  condensing  material  occupies  the  bend  B,  c, 
D,  if  liquid,  as  indicated  by  the  shaded  portion.  In  the  use  of  a 
solid  absorbent,  it  should  nearly  fill  both  legs  of  the  tube.  Very 
small  and  little  bottlings,  with  two  and  three  tubulures,  are  also 
used  for  delicate  operations. 

When  the  gas  is  to  be  generated  by  reaction  of  liquid  upon  a 
solid,  the  latter  must  be  put  into  the  flask  before  the  stopper  and 
tube  are  adjusted.  The  liquid  can  then  be  added  through  the  s 
tube,  as  often  as  it  is  required  to  continue  the  disengagement.  If 
the  gas  is  heavier  than  the  solvent  liquid,  the  disengagement-tube 
need  dip  but  slightly  beneath  its  level ;  and  vice  versd. 

There  are  several  points  to  be  remembered  in  the  generation 
and  collection  of  gases. 

1.  All  gases  owe  their  existence  as  such  to  a  certain  elasticity, 
by  reason  of  which  they  press  upon  the  sides  of  the  vessels  in 
which  they  are  enclosed. 

2.  The  tension  or  elastic  force  of  a  gas  is  proportional  to  its 
quantity :  it  augments  with  the  temperature,  and  decreases  by 
refrigeration. 

3.  The  atmosphere  weighs  upon  all  bodies,  its  pressure  being 


SAFETY-TUBES. 


359 


Fig.  298. 


usually  equal  to  the  weight  of  a  column  of  water  34  feet  high,  or 
of  a  column  of  mercury  30  inches. 

4.  That  liquids  (in  equilibrium)  press  equally  in  all  directions. 

These  facts,  therefore,  render  necessary  the  use  of  the  safety- 
tubes  <?,  c,  c,  Fig.  290,  and  Welters  tube,  Figs.  298,  299. 

Safety  Tubes.—  When,  in  the  course  of  distillation,  a  momen- 
tary suspension  of  the  heat  or  generat- 
ing impulse  causes  a  partial  vacuum  in 
the  heating  vessel,  the  liquid  into  which 
the  disengagement-tube  dips  is  forced 
by  the  pressure  of  the  atmosphere  into 
its  bore,  and  ultimately  into  the  vessel 
itself. 

This  entrance  of  liquid  into  the 
generating  vessel  may  result  also  from 
its  sudden  cooling,  by  the  entrance  of 
cold  water,  or  by  other  means. 

The  results  of  this  absorption  are 
sometimes  the  fracture  of  the  vessel, 

and  more  frequently  irreparable  injury  to  its  contents.  To 
obviate  these  inconveniences,  we  use  a  safety-tube,  the  usual 
forms  of  which  are  shown  by  Figs.  250,  298,  299.  The  first, 
which  is  called  an  s  tube  from  its  similarity  to  that 
letter,  is  most  used,  but  either  of  them  may  be  em- 
ployed in  the  following  manner.  If  the  generating 
vessel  has  only  one  aperture,  its  cork,  having  been 
tightly  fitted  and  rendered  impermeable  by  coatings 
of  sealing-wax  or  other  cement  on  its  upper  and 
lower  sides,  is  then  to  be  perforated  with  two  holes, 
one  for  the  transit  of  the  s  tube,  and  the  other  for 
that  of  the  exit  tube.  The  tubes  being  tightly  ad- 
justed in  the  holes,  as  shown  in  Fig.  298,  and  the  cork 
fitted  to  the  mouth  of  the  generating  flask,  a  quantity 
of  water  or  sometimes  of  other  liquids,  as  mercury,  is 
poured  into  the  s  tube.  When,  during  the  process, 
the  level  is  stationary  in  the  bulb  B,  and  in  the  part  A  of  the  tube, 
the  apparatus  is  hermetically  closed.  If,  however,  a  condensa- 
tion of  vapor  takes  place  in  the  interior  of  the  flask,  the  external 
pressure  of  the  atmosphere  weighs  alike  upon  the  liquid  F  of  the 


Fie.  299. 


360  GASOMETERS. 

trough,  and  that  in  the  s  tube  ;  but  as  the  latter  offers  the  least 
resistance,  the  air  first  makes  its  contained  fluid  advance  towards 
the  flask,  and  then  enters  in  bubbles  into  it,  thus  preventing  the 
absorption  of  liquid  from  the  trough  or  receiver. 

If  mercury  is  used,  its  relative  density  to  water  must  be  re- 
membered, and  the  column  of  metal  in  the  curve  should  be  as 
low  as  possible.  As  a  column  of  mercury  requires  one  of  water 
nearly  fourteen  times  its  height  for  its  support,  it  follows  that  if 
the  former  is  too  high,  the  gas  passes  back  more  rapidly  into  the 
recipient  during  condensation  from  the  disengagement-tube  than 
the  air  traverses  the  metallic  mass  in  the  s  tube.  Mercury  is 
used  when  the  Wolffe's  series  comprises  a  number  of  bottles  ;  so 
that  the  opposing  force  of  the  contained  liquid  may  not  be  suffi- 
cient to  cause  the  disengagement  of  the  gas  through  the  s  instead 
of  the  exit  tube.  When  operating  with  a  mercurial  trough,  the 
s  tube,  Fig.  299,  without  a  bulb,  is  used.  The  quantity  of  metal 
which  it  should  receive  must,  however,  be  such  that  the  pressure 
of  the  gas  will  meet  with  as  strong  a  resistance  from  it  as  the 
liquid  in  the  trough.  When  flasks  are  replaced  by  retorts,  the 
latter  should  be  tubulated,  so  that  the  safety-tube  may  be  adapted 
to  its  tubulure  by  means  of  a  perforated  cork. 

If  the  retorts  are  necessarily  plain,  as  in  certain  distillations  by 
furnace  heats,  then  the  safety-tube  can  be  attached  to  the  dis- 
engagement-tube E,  Fig.  307,  over  the  blowpipe  flame.  The 
liquid  is  introduced  at  H  i.  This  kind  of  tube,  known  as  Welter's, 
is  very  fragile,  and  requires  careful  management  and  handling. 

Gasometers.  —  When  the  eliminated  gas  is  to  be  preserved  free 
from  air,  in  large  quantities,  for  laboratory  purposes  or  transpor- 


is.  300. 


tation,  it  is  received  in  gasometers.    Gas  bags,  made  of  caoutchouc, 
are  very  convenient  for  storing  gas  for  use,  and  have  already 


PEPY'S   GASOMETER. 


361 


been  mentioned  at  p.  251.  The  annexed  drawing  presents  the 
apparatus  separately.  It  is  placed  between  two  hinged  boards, 
•with  a  hole  in  the  centre  of  the  joint  for  the  passage  of  the  neck 
of  the  bag  and  its  cock,  by  which  it  is  coupled  with  the  gene- 
rating apparatus,  as  seen  at  Fig.  171.  The  upper  board  is  fitted 
with  a  groove  for  the  reception  of  a  heavy  iron  upright,  which 
constitutes  the  pressure  by  which  gas  is  drawn  from  the  bag  as 
may  be  wanted. 

Pepy's  Gasometer. — The  most  convenient  gas-holder  is  that 
known  as  Pepy's,  Fig.  301.     It  consists  of  a  japanned  zinc  hollow 

Fig.  301. 


i  ! 
^             1  1 

ii 

h 

1  1 
•  ii 
a         MI 

ll 
II 
II 

ii 

^ 

L 

V   Y     \ 

cylinder  16  by  12  inches,  surmounted  by  a  trough  b  of  9  by  12 
inches,  making  the  total  height  of  the  apparatus,  including  that 
of  the  supports,  three  feet.  Near  the  base  of  the  cylinder  is  a 
lateral  gulley,  placed  obliquely,  and  cut  with  a  thread  to  receive  a 
screw  plug,  which  closes  it  hermetically. 

The  tube  d,  supporting  the  centres  of  the  vessels,  and  fitted 
with  a  cock,  allows  a  communication  between  the  reservoir  and 
trough.  A  second  tube  *  c  i,  at  the  side,  also  fitted  with  a  cock, 
passes  from  the  upper  cylinder  into  the  lower,  and  descends,  as 
shown  by  the  dotted  lines,  to  within  a  few  lines  of  the'  bottom. 
The  stem  e  is  merely  a  support,  and  serves  no  other  purposes. 
The  coupling  and  stop-cock  in  the  side  near  the  top  serve  for 
connection  with  a  jet,  or  for  fitting  on  a  bag  or  bladder.  The 


362  PEPY'S  GASOMETER. 

glass  gauge  Jc,  graduated  into  cubic  inches,  is  adjusted  firmly  and 
hermetically  by  means  of  sockets  at  the  top  and  bottom  of  the 
cylinder,  and  serves  to  indicate  the  level  of  the  internal  water. 
To  prevent  fracture,  it  is  embedded  in  a  framework  of  the  same 
metal  as  the  gas-holder. 

The  manner  of  using  the  apparatus  is  as  follows : — close  the 
mouth  #,  and  fill  the  reservoir  with  water.  For  this  purpose  the 
water  is  poured  into  the  trough  5,  and  allowed  to  run  down 
through  the  opened  tubes  d  and  c.  The  cock  /  being  also  opened, 
the  confined  air  escapes  as  the  water  enters,  and  in  proportion 
as  the  reservoir  a  is  filled,  the  water  rises  in  the  tube  k,  and 
hence  the  latter  will  indicate  when  it  is  full.  As  soon  as  this 
occurs,  and  water  runs  through  the  pipe  /,  the  cock  of  the  latter 
must  be  closed,  and  the  residual  air  allowed  to  escape  through 
the  still  open  tube  d.  If,  upon  gently  shaking  the  vessel,  no 
more  bubbles  appear,  then  all  the  cocks  are  to  be  closed,  and  the 
apparatus  mounted  over  a  tub,  of  diameter  some  six  inches  or 
more  greater  than  that  of  the  gasometer,  and  the  gullet  g  is  then 
opened.  As  the  highest  part  of  the  edge  of  the  inner  aperture 
of  this  gullet  is  lower  than  the  lowest  part  of  the  edge  of  the 
outer  aperture,  by  a  half  inch  or  more,  the  water  cannot  escape, 
unless  the  air  simultaneously  finds  access,  inwards,  from  above, 
by  leak-holes  or  otherwise.  If,  after  the  gush  of  a  small  portion 
when  the  plug  is  first  removed,  there  should  be  any  further 
leakage,  it  will  be  indicated  by  the  gauge-tube. 

All  being  tight,  the  beak  of  the  retort,  or  end  of  the  conduit- 
tube  of  the  generating  vessel,  is  introduced  into  the  gullet,  as 
shown  at  A,  Fig.  302.  The  eliminating  gas  entering  the  receiver, 
displaces  the  water,  which  escapes  at  #,  and  falls  into  the  pail 
beneath.  As  soon  as  the  vessel  is  full,  which  will  be  known  by 
the  examination  of  the  gauge,  or  when  a  sufficient  quantity  has 
been  collected,  the  disengaging-tube  or  beak  is  withdrawn,  and 
the  gullet  closed  with  the  plug. 

If  it  is  desired  to  fill  a  gas-bag  from  the  reservoir,  it  must  be 
fitted  with  an  appropriate  cock  and  nipple  for  connecting  with 
the  coupling  cock  /,  and  the  pressure  of  the  water  with  which  the 
trough  b  has  been  partially  filled,  should  be  made  to  act  upon 
the  gas  by  opening  the  cock  c.  So  also  when  the  gas  is  to  be 
transvased  into  bell-glasses,  these  latter  are  filled  with  water  to 


MERCURIAL  GASOMETER.  363 

displace  all  air,  inverted,  and  then  brought  directly  over  the 
opened  tube  d,  as  shown  in  Fig.  302.  As  the  water  enters  from 
the  trough  through  the  tube  <?,  gas  escapes  into  the  jar  by  the 
exit  pipe  d.  When  the  vessel  is  filled,  communication  must  be 
shut  off  by  closing  the  cocks. 

When  a  greater  pressure  is  required  than  can  be  given  by 
the  water  contained  in  the  trough,  it 
can  be  obtained  by  means  of  a  long-  Fig.  303. 

barrelled  funnel  0,  Fig.  304.  When 
this  is  screwed  by  its  threaded  nipple  p, 
into  the  socket  s,  Fig.  302,  and  filled 
with  water,  there  is  a  pressure  of  nearly 
six  feet.  By  abridging  the  length  of 

the  barrel  to  q,  the  pressure  is  diminished  to  a  little  less  than 
four  feet.  When  two  of  these  gasometers,  filled  the  one  with 
oxygen  and  the  other  with  hydrogen,  are  united  by  means  of  a 
double  jet,  Fig.  303,  connected  by  its  branches  a  b  with  the  cocks 
f  of  the  reservoir,  they  form  what  is  called  the  hydro-oxygen  or 
COMPOUND  BLOWPIPE  described  at  p.  170. 

Mercurial  Gasometer. — When  the  eliminated  gas  is  soluble  in 
water,  or  altered  by  contact  with  that  liquid,  it  may  with  pro- 
priety be  collected  over  mercury.  For  this  purpose  Pepy  has 
contrived  the  arrangement  shown  in  Fig.  305,  which  obviates  the 
expense  and  inconvenience  of  filling  the  cistern  with  mercury. 
It  is  made  of  iron,  and  consists  of  a  bell  A  A  B  B,  which  has  a 
cock  c  at  its  summit,  and  which  is  immersed  in  a  cylindrical  iron 
cistern  M  N  o  p.  This  cistern  is  the  reservoir  for  the  mercury, 
but  in  order  that  as  little  as  possible  may  be  used,  an  iron  core 
D  E  occupies  its  centre,  and  allows  an  interval  between  it  and  the 
sides  of  the  cistern  only  sufficient  for  the  jar  and  mercury  to 
make  it  tight.  A  glass  tube  a  b  cemented  tightly  to  the  top  of 
this  inner  cylinder,  traverses  it  and  serves  as  a  conduit  of  the 
gas  into  the  bell,  which  is  maintained  in  a  vertical  position  by  a 
movable  elbow  adjusted  to  the  frame  of  the  apparatus. 

A  cock  c  is  adjusted  to  the  tube  a  b,  and  puts  it  in  communi- 
cation with  the  eprouvette  or  small  inverted  bell  F,  placed  upon 
a  dish  containing  mercury. 

In  using  this  gasometer,  the  cavity  M  N  0  P  is  filled  with 
mercury,  the  cocks  c  and  c  are  opened,  and  after  the  bell  has 


364 


MERCURIAL  GASOMETER. 


been  pressed  down  to  its  full  extent  in  the  metal,  the  cock  c  is 
closed. 

The  disengagement-tube  is  then  introduced  under  the  mouth 
of  the  eprouvette,  and  the  generation  of  the  gas  proceeded  with. 


Fig.  304. 
3. 


Fig.  305. 


Each  bubble  as  it  enters  the  bell  elevates  it  proportionately ;  and 
when  it  has  received  a  quantity  equivalent  to  the  volume  of  the 
capacity  of  the  tube  and  of  the  eprouvette,  the  cock  c  is  to  be 
opened  again  and  the  bell  depressed.  The  greater  part  of  the 
gas  which  has  entered,  and  the  air  with  which  it  is  mixed,  is  thus 
forced  to  escape.  A  repetition  of  this  manoeuvre  two  or  three 
times  will  insure  the  entire  expulsion  of  the  air ;  when  the  por- 
tions of  gas  given  off  can  be  collected  and  preserved  for  use. 
When  the  bell  is  full,  the  cock  c  is  to  be  closed  and  the  retort  J 
removed. 

To  transvase  any  portion  of  the  gas  that  may  be  wanted  for 
use,  it  is  only  necessary  to  put  the  tubulure  c  in  communication 
with  the  vessel  in  which  it  is  to  be  received,  by  opening  the  cock, 
and  then  to  depress  the  bell  in  the  mercury. 


PNEUMATIC  TROUGHS. 


365 


Fig.  306. 


A  scale  graduated  upon  the  side  of  the  bell  will  allow  an  esti- 
mation of  the  volume  expended. 

Devilles  Gasometer.— Thia  apparatus,  constructed  upon  the 
same  principle  as  Harriot's  vase,  is  most  used  in  organic  analysis. 
Fig.  306  exhibits  the  arrangement.     A  A  is  a  tubulated  bottle 
filled  with  water ;  and  a  a  a  is 
the   tube   for   disengaging    the 
gas  from  the  generator.     Each 
bubble  of  gas  displaces  an  equal 
volume  of  water,  which  is  con- 
ducted  off    by  means    of   the 
syphon  b  b  b,  and  the  process 
should  be  continued   until  the 
expulsion  of  all  the  water,  save 
just  enough  to  fully  close  the 
orifices  of  the  tube. 

When  the  gas  is  to  be  dis- 
engaged for  use,  fill  the  funnel 
E  with  water,  and  open  the  cock 
f.  The  pressure  of  the  water 
descending  into  the  flask  forces 
the  gas  into  the  tube  i  i. 

A  flexible  tube  H  I  can  then 

be  adapted  to  the  orifice  of  the  vessel  into  which  the  gas  is  to  be 
introduced. 

This  gasometer  is  especially  employed  for  holding  oxygen  to 
be  passed  over  oxide  of  copper  in  tubes,  after  organic  analysis ; 
and  to  remove  all  carbonic  acid  that  it  may  contain,  it  is  passed 
through  a  flask  containing  an  aqueous  solution  of  caustic  potassa. 

The  small  bottle  c  contains  the  concentrated  sulphuric  acid, 
and  the  tube  u  potassa  in  one  branch,  and  chloride  of  calcium  in 
the  other. 

If  the  oxygen  is  kept  in  this  holder  for  too  long  a  time,  it 
becomes  altered  and  contaminated  with  atmospheric  air. 

PNEUMATIC  TROUGHS. — In  most  manipulations  with  gases, 
particularly  when  they  are  required  for  immediate  use  or  for 
temporary  purposes,  they  are  collected  over  the  pneumatic 
trough.  As  the  bell  glasses  into  which  they  are  to  be  received 
must  first  be  freed  from  contained  air,  it  is  necessary  to  immerse 


WATER  TROUGH. 


them  in  an  appropriate  liquid.  Water  and  mercury  are  the  two 
fluids  almost  universally  employed,  the  first  being  used  for  all 
those  gases  which  are  not  soluble  in  it,  and  for  some  which  are 
only  so  in  a  slight  degree,  and  the  latter  for  those  which  are 
absorbed  by  water,  and  which  exert  no  chemical  action  upon  the 
mercury.  Hence  the  distinctive  terms,  water  and  mercurial 
trough. 

Water  Trough. — A  wooden  pail,  square  or  oval,  with  a  little 
management,  can  be  converted  into  a  most  convenient  water 


trough,  G,  Fig.  307.  It  should  be  of  capacity  sufficient  to  allow  the 
thorough  immersion  of  bells  of  any  size  required  for  experiment. 
One  of  a  foot  in  depth,  sixteen  inches  in  length,  and  ten  inches 
in  width,  will  be  very  suitable, — a  vessel  G  of  this  size  fulfilling 
almost  all  the  requirements  of  an  experimental  laboratory.  Near 
to  the  top,  in  the  interior,  should  be  lateral  flanges  for  the  sup- 
port of  a  sliding  shelf  a.  This  sliding  shelf  should  have  sufficient 
surface  for  the  support  of  several  bells  or  jars,  F,  at  a  time,  and 
may  extend  over  half  of  the  trough.  It  is  perforated  with  holes 
for  the  reception  of  the  beak  of  the  disengaging 
vessel,  as  seen  at  5,  Fig.  306. 

A  very  convenient  water-bath  for  the  collec- 
tion of  gases  may  be  formed  of  a  deep  earthen- 
ware dish,  or  other  vessel  in  common  use,  by  the 
addition  of  the  bee-hive  shelf,  Fig.  308.  This 
shelf,  generally  made  of  porcelain,  is  a  substitute  for  the  shelf  of 
a  regular  trough,  and  serves  for  the  support  of  the  bell  glasses  or 


Fig.  308. 


BELL  GLASSES — GAS  JARS.  367 

other  receivers.  It  may  be  two  inches  in  diameter  and  one  inch 
high,  for  a  dish  one  foot  wide  and  two  inches  deep,  and  propor- 
tionally larger  for  one  of  greater  dimensions.  The  disengage- 
ment-tube enters  the  semicircular  opening  at  the  base,  and 
delivers  the  gas  into  the  receiver  by  its  curved  end  protruding 
through  the  hole  in  the  centre.  Part  of  a  loaded  wooden  box, 
a  metallic  support,  or  other  extemporaneous  arrangement,  may, 
in  many  cases,  be  so  adjusted  to  take  the  place  of  the  common, 
or  the  bee-hive  shelf,  and  to  answer  every  useful  purpose. 

It  is  indispensable  that  the  trough  should  be  made  thoroughly 
water-tight,  and  should  be  well  hooped.  For  further  protection, 
it  might  be  covered  over  with  several  coats  of  paint.  Leakage 
being  thus  provided  against,  the  vessel  may  be  used  upon  either 
the  operating  or  centre  table.  The  stop-cock  near  the  bottom 
allows  the  exit  of  the  water  when  it  has  become  dirty,  acidified,- 
or  otherwise  unfit  for  use. 

The  level  of  the  contained  water  must  always  be  half  an  inch 
or  more  above  the  top  of  the  shelf.  When  the  bell  is  to  be 
charged,  it  is  first  completely  immersed  in  the  water,  so  as  to 
expel  all  contained  air,  then  taken  up  by  the  knob,  raised  to  a 
vertical  position,  and  carefully  slid  along  with  its  mouth  in  the 
water  to  the  shelf,  and  placed  immediately  over  the  hole  through 
which  the  disengagement-tube  enters.  As  the  gas  bubbles  up 
into  the  bell,  the  water  is  displaced,  and  when  it  is  filled,  it  can, 
if  necessary,  be  drawn  aside  and  replaced  by  another.  So  the 
process  is  continued  until  all  the  gas  generated  has  been  col- 
lected in  bells. 

As  the  first  bubbles  of  gas  eliminated  are  contaminated  with 
air,  they  should  be  rejected ;  consequently  the  beak  of  the  dis- 
engagement-tube ought  not  to  be  brought  under  the  bell  receiver 
until  the  gas  commences  to  pass  over  freely. 

Bell  Glasses— G-as  Jars  or  Eeceivers.—The  arrangement  of  an 
experimental  laboratory  is  incomplete  without  a  series  of  bell 
glasses,  varying  in  size  from  a  gill  upwards  to  one  gallon.  They 
should  be  of  glass,  preferably  of  white  glass  free  from  lead,  and 
made  so  as  to  combine  strength  and  neatness,  and  should  have 
a  knob  at  the  summit  for  convenience  of  handling.  The  rim 
of  the  mouth  must  be  ground  perfectly  smooth  and  level,  so 
that  when  resting  upon  an  unground  glass  disk  or  an  even-hot- 


368 


BELL   GLASSES — GAS  JARS. 


tomed  plate,  the  joint  may  be  tight.     Fig.  309  exhibits  a  plain 
jar  for  ordinary  uses ;  and  Fig.  310  a  similar  implement  tubu- 


Fis.  309. 


Fig.  310. 


Fiz.  311. 


lated  at  its  summit,  and  closed  with  a  glass  stopper.  This  open- 
ing not  only  allows  the  facility  of  forming  connections  with  other 
apparatus,  but  also  that  of  filling  it  readily  with  liquid  merely  by 
depressing  it,  while  unstopped,  vertically  in  the  water  trough. 
The  air  escapes  through  the  tubulure  in  proportion  to  the  rise  of 
fluid  in  the  receiver,  which  when  full  is  to  be  stoppered  and  placed 
upon  the  shelf  to  receive  the  gas.  Sometimes  the  tubulures  are 
fitted  with  stop-cocks,  as  seen  at  Fig.  311,  which 'add  to  the  con- 
venience of  the  jars  in  many  operations,  and  particularly  when  it 
is  desired  to  pass  a  measured  quantity  of  gas  from  the  receiver 


Fig.  312. 


Fig.  313. 


into  another  vessel  attached  as  heretofore  described  at  p.  147. 
For  this  purpose  the  bell  must  also  be  graduated  as  seen  in  Fig. 
312.  Fig.  313  presents  a  graduated  bell-tube. 


THE  MERCURY  TROUGH.  369 

If  the  vessel  into  which  the  gas  is  to  be  received  is  a  bladder 
instead  of  a  glass  bell,  it  must  be  fitted  with  a  coupling  cock, 
freed  from  air  as  much  as  possible  by  compression  with  the  hands, 
then  connected  with  air-pump  or  syringe,  and  completely  exhausted 
by  suction.  The  cock  is  then  closed,  the  bladder  detached  from 
the  syringe,  and  adapted  by  its  coupling  to  the  cock  of  the  bell. 
Communication  being  opened,  the  gas  passes  into  the  bladder 
Upon  the  depression  of  the  jar. 

By  grinding  the  surface  of  the  ledge  very  accurately,  and  fit- 
ting the  mouth  of  the  bell  with  a  ground  glass  disk,  which,  by 
the  intervention  of  a  little  grease,  may  form  an  air-tight  joint, 
gases  may  be  retained  unaltered  for  a  limited  period.  The 
syringe,  Fig.  47,  is  made  so  that  it  may  be  used  both  vertically 
and  horizontally. 

The  Mercury    Trough. — The   high  cost  of  mercury  renders 
necessary  an  economical  construc- 
tion of  the  trough  in  which  it  is     Fig-  314' 

kept.  Fig.  314  exhibits  one  of 
convenient  form.  It  consists  of 
a  well-japanned  cast-iron  trough, 
twelve  inches  long,  seven  inches 
wide,  and  two  inches  deep.  The 
bottom,  towards  the  side,  is  sunk 
throughout  its  length  into  a  well 
two  inches  wide  and  one  and  three- 
quarter  inches  deep,  and  is  ex- 
panded at  its  end  into  a  circular 
cavity.  This  cavity  allows  of  the 
immersion  of  the  tubes  or  bells  in 

a  moderate  depth  of  mercury  without  the  expense  of  filling  the 
whole  trough  being  incurred ;  and  the  circular  end  being  larger 
than  the  other  portion  of  the  canal,  allows  the  use  of  receivers  of 
from  two  to  three  inches  in  diameter. 

When  this  cavity  is  not  in  use  and  the  mercury  required  to  fill 
it  is  needed  in  the  other  part  of  the  trough,  it  is  closed  with  an 
exactly  fitting  iron  plug  which  accompanies  the  vessel  for  this 
purpose. 

The  trough  is  placed  upon  the  operating-table,  and  is  manipu- 
lated with  in  the  same  manner  as  the  water  trough.  For  the 

24 


370 


THE    MERCURY    TROUGH. 


convenience  of  supporting  tubes  in  a  vertical  position,  there  is  an 

accompanying   clamp  with 
sliding    rod,   which    is 


Fig.  3 15. 


at- 


tached to  the  side. 

The  small  mercurial 
trough  of  porcelain,  Figs. 
315,  317,  very  useful  in  or- 
ganic analysis,  contains  usu- 
ally from  ten  to  twelve 
pounds,  and  serves  also  very 
conveniently  for  experi- 
ments upon  a  small  scale. 

Smaller  sizes,  of  about  four  pounds  capacity,  are  made  after  the 
pattern,  Fig.  316. 

Fig.  318  exhibits  a  cylindrical  glass  trough, 
which  is  used  with  tubes  in  organic  analysis. 
It  is  of  glass,  fifteen  and  a  half  inches  high, 
and  is  widened  at  the  top.      The  drawing 
represents  the  introduction  of  lye  into  a  graduated  tube  by  means 


Fig.  316: 


Fig.  317. 


Fig.  318. 


Fig.  319. 


of  the  pipette,  Fig.  319,  over  a  column  of  mercury.    The  tip  of  the 


THE  MERCURY  TROUGH.  371 

pipette  is  curved  so  as  to  facilitate  its  entrance  under  the  mouth 
of  the  tube.  This  plan  is  adopted  sometimes  in  lieu  of  that  given 
at  p.  353,  for  the  separation  of  two  gases,  by  presenting  to  both 
a  third  substance  for  which  either  of  them  has  an  affinity. 

Griffin's  trough,  which  is  designed  for  working  with  long  tubes 
and  the  least  possible  quantity  of  mercury,  has  the  form  of  the 
annexed  drawings,  the  lower  one  of  which  presents  a  sectional 
view. 

Fi?.  320. 


It  has  a  permanent  bee-hive  shelf  a  a  for  supporting  tubes  in 
the  act  of  being  filled  with  gas,  and  a  space,  which  allows  liquids 
to  be  passed  in  a  small  tube,  through  the  mercury,  to  the  gas. 

Mercury  troughs  are  generally  made  of  iron,  stoneware,  or 
porcelain ;  but  we  prefer  them  of  some  hard  and  very  smooth 
wood.  The  root  of  the  apple-tree  fulfils  all  the  requirements ; 
and  a  carver  will  fashion  a  neat,  durable,  and  cleanly  trough 
from  a  single  piece.  It  is,  however,  advisable  to  have  the  upper 
part  of  the  sides  made  of  thick  glass  plate,  set  firmly  in  grooves 
by  means  of  cement.  This  arrangement  permits  the  level  of  the 
metal  in  the  tube  to  be  seen  at  the  lowest  points. 

In  the  course  of  time  the  mercury  of  the  trough  becomes  de- 
based by  use,  either  with  water,  metals,  or  suspended  matters. 
The  water  being  specifically  lighter,  may  very  readily  be  removed 
by  spreading  sheets  of  bibulous  paper  on  the  surface  of  the  mer- 
cury, and  renewing  them  as  fast  as  they  become  saturated.  The 
metals  are  separable  by  distillation,  the  mercury  passing  over 
pure  into  the  recipient. 


372  TRANSFER   OF  GASES. 

If  the  impurities  are  merely  coarse  suspended  particles,  as  of 
metallic  oxides,  straining,  by  compression  with  the  hands,  through 
a  chamois  leather  bag,  will  retain  them,  and  even  most  amal- 
gams, while  the  mercury  passes  through  the  pores  entirely  or 
almost  pure. 

Gases  Collected  over  Air. — Although  chlorine  can,  for  tempo- 
rary purposes,  be  collected  over  hot  water  in  which  it  is  not 
dissolved,  that  body,  as  well  as  iodhydric  and  bromhydric  acids, 
and  certain  other  gases  which  are  soluble  in  water,  or  which 
attack  mercury,  are  sometimes  collected  in  receivers  or  bottles 
filled  with  air. 

If  the  gas  is  lighter  than  air,  the  end  of  the  disengagement- 
tube  should  reach  to  the  upper  part  of  the  inverted  vessel.  As 
the  gas  enters,  the  air  is  displaced  and  goes  out  below,  and  the 
jar  is  known  to  be  full  when  the  gas  also  escapes.  The  jar  must 
then  be  slowly  and  carefully  removed,  so  that  the  vacuum  left  by 
the  withdrawal  of  the  tube,  may  be  completely  supplied  by  the 
gas  simultaneously  entering,  and  its  mouth  be  closed  with  a  plate 
of  ground  glass,  cork,  piece  of  caoutchouc,  or  other  suitable 
means. 

When  the  gas  is  heavier  than  air,  as  is  the  case  with  chlorine, 
the  disengagement-tube  should  enter  to  the  bottom  of  the  re- 
ceiver, the  mouth  of  which  should  be  closely  covered  with  a  paste- 
board disk.  When  the  gas  begins  to  escape  at  the  mouth,  the 
jar  is  full,  and,  after  being  closed  with  a  ground  glass  plate  or 
other  stopper,  carefully  removed  aside. 

Transfer  of  Grases. — It  is  frequently  necessary  to  transfer 
portions  of  gas  from  a  large  vessel  to  a  smaller  one  for  the  pur- 
poses of  experiment  or  MEASUREMENT.1  Having  already  given 

1  As  the  volume  of  gas  confined  in  tubes,  or  other  vessels,  over  mercury  or 
water  varies  according  to  the  pressure  of  the  surrounding  atmosphere,  it  becomes 
necessary  in  experiments  on  gases  to  observe  the  barometric  pressure,  or  the  height 
of  the  mercurial  column  in  the  barometer,  at  the  time  the  volume  of  the  gas  is 
observed.  Every  laboratory  ought,  therefore,  to  be  provided  with  a  barometer, 
which  should  either  be  a  good  syphon-barometer  or  a  cistern-barometer,  in  which 
the  mercury  of  the  cistern  may  be  brought  to  the  same  level  before  observing  the 
height  of  the  column.  The  latter  is  generally  read  off  in  a  scale  divided  into 
inches,  tenths,  and  hundreds  of  inches.  As  the  height  of  the  mercurial  column 
varies  according  to  the  temperature,  a  correction  must  be  made  for  the  tempera- 
ture of  the  mercury  in  the  barometer,  which,  for  this  purpose,  is  furnished  with  a 
thermometer  to  be  observed  at  the  same  time. 


TRANSFER  OP  GASES. 


373 


the  mode  of  transferring  from  a  gasometer,  we  will  now  speak  of 
transvasement  over  troughs. 

If  the  jar  or  reservoir  of  gas  is  still  upon  the  shelf  of  the  pneu- 
matic trough,  the  smaller  vessel,  which  is  to  receive  a  portion  of 
its  contents,  is  to  be  entirely  immersed  in  the  fluid  of  the  trough, 
and,  whilst  full,  conveyed  bottom  downwards  to  the  shelf,  and 
there  placed  so  that  it  will  project  over  the  edge  of  about  a  third 
of  its  diameter.  The  reservoir  is  then  brought  forward,  and  the 
mouths  of  the  two  put  in  connection,  as  shown  in  Fig.  321,  by 

Fig.  321. 


inclining  the  reservoir  so  that  their  edges  may  be  in  contact: — 
the  gas  then  passes  up  in  bubbles,  and  by  a  little  dexterity  the 
rapidity  of  its  flow  can  be  easily  regulated. 

At  pages  126,  202,  and  203,  we  have  already  given  directions 
for  the  transfer  of  gases  into  tubes  and  globular  vessels. 

Bladders  are  filled  from  the  cocked  receivers,  Fig.  312,  aa 
directed  at  p.  368.  Bladders  are  cleansed  by  ablution  in  weak 
potash  lye,  subsequent  washings  in  fresh  water  and  drying. 
The  caoutchouc  bags,  mentioned  at  p.  304,  are,  however,  pre- 
ferable. 

When  the  filled  receiver  is  to  be  removed  from  the  trough  for 
further  essays  with  gas,  it  should  be  gently  slid  off  the  shelf  into 
a  flat-bottomed  plate  containing  just  enough  water  or  mercury  to 
seal  the  mouth. 

Distillation  ly  Steam. — Steam  is  a  most  convenient  as  well  as 
efficient  means  of  distillation  in  a  large  number  of  cases.  For 
example,  in  the  distillation  of  essential  oils,  and  similar  volatile 


374  DISTILLATION  IN  VACUO. 

substances,  separable  from  fixed  matter  by  a  heat  of  212°  to 
230°  F.  The  application  of  the  steam  must  be  direct,  and  pro- 
vision for  its  use  in  this  manner  has  been  made  at  A  in  our  design 
of  the  steam  series,  Fig.  18.  The  solid  matters  rest  in  the  body 
of  the  vessel  upon  a  perforated  lining  or  diaphragm,  and  the 
steam  is  led  into  the  interior  through  a  pipe  ending  in  a  cullen- 
der, so  as  to  cause  its  diffusion  throughout  the  mass.  To  prevent 
loss  of  heat  by  radiation,  the  sides  of  the  containing  vessel  should 
be  wrapped  in  woollen.  As  the  volatile  substance  is  eliminated 
from  its  fixed  associates,  it  becomes  involved  with  the  arising 
steam,  and  passes  over  into  the  condenser,  and  ultimately  into 
the  receiver,  where  the  two  form  distinct  layers  according  to  their 
differing  densities ;  and  the  water,  or  condensed  steam,  may  be 
thus  separated  from  the  valuable  product,  as  directed  at  p.  340. 

By  passing  the  steam  through  hot  tubes  before  its  admission 
into  the  still  or  other  containing  vessel,  it  may  be  superheated 
to  a  very  high  degree,  and  in  this  state  becomes  a  powerful  de- 
composing agent ;  and  consequently  useful  for  those  distillations 
in  which  the  required  distillate  is  to  be  formed  from  the  decom- 
position of  the  original  matter  under  process.  The  matters 
treated  in  this  way  are  generally  contained  in  metallic  vessels 
and  tubes  capable  of  resisting  a  certain  amount  of  pressure.  The 
superheated  steam  is  led  directly  into  and  through  them ;  so  that 
the  distillate  becomes  incorporated  with  the  aqueous  vapors,  and 
passes  out  with  the  latter  into  the  condenser  and  receiver. 

DISTILLATION  IN  VACUO. — This  kind  of  distillation  is  resorted 
to  for  the  production  or  purification  of  many  volatile  matters 
which  are  alterable  in  the  air  or  in  aqueous  vapor.  Retorts 
drawn  out  at  their  beak  into  a  very  narrow  opening,  or  glass 
tubes,  fashioned  over  the  blowpipe  flame  to  suit  the  process,  are 
the  vessels  commonly  employed.  After  the  vessel  is  charged, 
heat  is  applied  to  the  bulb  portion,  and  as  soon  as  it  becomes 
filled  with  vapor  and  all  air  is  expelled,  the  tube  should  be  heated 
over  a  lamp.  After  the  annealing  of  the  closed  end,  it,  being 
intended  for  the  reception  of  the  distillate,  should  be  exposed  to 
the  influence  of  cold  while  the  process  is  being  conducted.  If 
the  retort  is  used,  the  receiver  with  which  it  is  connected  must 
be  warmed  over  the  sand-bath,  and  in  delicate  experiments  ex- 
hausted by  means  of  the  syringe,  Fig.  99,  or  air-pump,  Fig.  47. 


DRY   OR  DESTRUCTIVE  DISTILLATION. 


375 


Fig.  322. 


Dry  or  Destructive  Distillation. — This  kind  of  distillation  has 
a  more  general  application  to  solids  than  liquids ;  but,  in  either 
case,  the  substances  under  treatment  are  highly  heated,  in  close 
vessels,  until  decomposition  en- 
sues, for  the  sake  of  the  pro- 
ducts  thus   generated.      These 
products  are  mostly  the  distil- 
late, which  is  either  gaseous  or 
liquid,  or  both  simultaneously; 
but  in  rare  instances,  the  resi- 
duum in  the  retort  is  the  de- 
sirable matter.     The  operation 
is  practised  for  the  decomposi- 
tion of  certain  kinds  of  bodies, 
particularly    those    of    organic 
nature.     The  new  compounds  are  formed  by  an  interchange  of 
the  ultimate  components  of  the  original  body  under  the  influence 
of  heat.     The  process  for  organic  analysis  is  a  veritable  destruc- 
tive distillation,  and  has  already  been  described  at  p.  247.     The 
tubes  for  this  and  similar  experiments  being  long,  require  the 
use  of  the  gas  furnace,  Fig.  166,  for  heating  them.     The  product 
in  that  case  being  gaseous,  is  either  absorbed  by  a  suitable  liquid, 
as  shown  by  Fig.  139,  or  received  over  mercury,  as  seen  in  the 
annexed  drawing. 

Fig.  323. 


When  the  distillate  is  both  gaseous  and  liquid  at  the  same  time, 
the  generating  apparatus  must  have  two  receiving  vessels  con- 
nected  with  it,  one  adapted  to  the  absorption  of  the  gas,  and  the 
other  for  the  condensation  of  the  liquid. 

The  vessels  in  which  dry  distillation  is  performed  are  mostly 


376  DRY   OR  DESTRUCTIVE   DISTILLATION. 

of  iron,  and  occasionally  of  porcelain  and  earthenware ;  but,  in 
either  case,  the  covers  must  be  movable  for  convenience  of  remov- 
ing the  residuum,  which,  being  very  often  dry  and  hard,  adheres  to 
the  bottom  of  the  retort  with  great  tenacity.  Earthenware  and 
porcelain  retorts  are  only  used  in  very  exact  experiments,  for 
which  those  of  metal  are  not  well  adapted.  Those  of  porcelain 
are  expensive  and  very  fragile ;  while  the  earthenware  retorts, 
though  much  less  costly,  are  only  less  apt  to  crack  during  the 
heating.  The  usual  form  is  seen  at  Fig.  322,  which  shows  the 
head  detached  from  the  body.  The  two  are  cemented  together 
by  lute,  when  under  process,  so  as  to  form  a  steam-tight  joint. 

Iron  retorts  have  already  been  de- 
Fig.  324.  scribed  at  p.  332,  and  another  form  is 
now  presented  in  Fig.  324,  which  shows 
one  with  its  head  fitted  to  the  body  by 
ground  joints,  and  held  securely  in  place 
by  a  clamp  and  screw. 

As  examples  of  the  effect  of  dry  distil- 
lation upon  certain  substances,  citric  acid 
may  be  converted  by  it  into  carbonic  acid 
and   oxide,  acetone,  aconitic   acid,  and 
water;  fatty  bodies   modified  into  new 
substances ;  and  resins  transformed  into 
oily  liquids  and  gaseous  carbohydrogens. 
In  the  dry  distillation  of  nitrogenized  bodies,  the  resultant 
products  are  complex,  and  contain  nitrogen,  ammonia,  cyanogen, 
&c.     For  instance,  indigo  yields  carbonate  and  prussiate  of  am- 
monia and  kyanole. 

In  the  arts,  the  dry  distillation  of  wood  furnishes  charcoal, 
pyroligneous  acid,  pyroxylic  spirit,  creasote  and  tar;  and  that  of 
bituminous  coal  and  fat,  illuminating  gas. 

The  employment  of  close  vessels  in  distillations  is  becoming 
very  general  for  certain  classes  of  experiments.  They  present 
the  great  advantage  of  excluding  the  air  from  the  interior ;  and 
afford  the  means  of  exciting  reaction  in  substances  which  would 
otherwise  vaporize,  and  escape  under  atmospheric  pressure. 
Moreover,  the  internal  pressure  thus  created,  is  a  condition 
which  favors  the  action  of  the  heat  in  augmenting  the  affinities 


HEATING   IN   CLOSE   VESSELS.  377 

of  the  elements  of  the  substance  under  process  of  destructive 
distillation. 

Berthelot's  suggestions  (Journ.  Pharm.  et  Chim.  XXIII),  in 
regard  to  the  proper  mode  of  managing  close  vessels,  in  heating 
operations,  are  so  full  of  serviceable  instruction,  that  we  annex 
an  abstract. 

For  temperatures  below  212°  F.,  the  containing  vessels  may- 
be heated  by  water-bath,  which  should  be  covered  to  prevent  the 
spattering  of  the  boiling  water.     For  212°  F.  to  750°  F.,  the 
heating  medium  must  be  an  oil-bath  in  a  close  vessel,  the  neces- 
sary precautions  being  observed  to  prevent  explosions  by  the 
ignition  of  the  boiling  oil  or  its  vapor.     To  this  end  the  boiler 
should  not  be  filled  to  more  than  .half  its  depth  with  oil,  and 
should  rest  by  a  flange  upon  its  circumference,  and  midway  from 
the  bottom  upon  the  top  of  a  strong  and  close  chamber,  surmount- 
ing a  furnace,  the  fire-hole  of  which  must  have  its  entrance  upon 
the  outside  of  the  apartment.     The  fire-grate  should  be  about  23 
inches  from  the  bottom  of  the  boiler.     The  boiler  itself  should  be 
about  2J  feet  in  height  and  slightly  conical,  and  should  be  enve- 
loped with  a  brickwork  casing,  so  as  to  shut  off  all  communication 
between  it  and  the  fire,  except  by  means  of  the  furnace  part.     To 
indicate  the  temperature  of  the  oil,  a  long  thermometer  is  ad- 
justed in  a  hole  in  the  top.     For  heating,  glass  tubes  should  be 
confined  in  iron  tubes,  closed  at  one  end  by  hammering,  and  at 
the  other  with  a  screw  plug ;  this  arrangement  prevents  the  spat- 
tering of  the  oil  in  the  event  of  the  glass  tube  breaking,  though 
in  some  rare  cases,  as  in  the  heating  of  alcohol  to  750°,  the  ex- 
plosion of  the  glass  tube  is  so  violent  as  even  to  break  the  iron 
envelop,  and  the  inflammable  gases  thus  projected  through  the 
heated  oil  are  liable  to  take  fire.     When  such  a  contingency  is  to 
be  apprehended,  the  iron  tube  should  also  be  enveloped  in  a  tight 
sheet-iron  muff,  for  the  purpose  of  confining  the  inflammable  gases 
in  case  of  accident.    The  whole  is  then  immersed  perpendicularly 
in  the  bath,  so  that  its  entire  length  may  be  covered  during  the 
heating.     The  oil  for  the  bath  should  be  prepared  by  boiling  it  in 
the  open  air  until  it  has  acquired  an  almost  solid  consistence 
when  cold.     In  this  state  it  can  be  heated  to  above  680°  without 
sensible  ebullition.     After  having  been  used  continuously  for 


378  HEATING  IN   CLOSE  VESSELS. 

several  days,  the  oil  is  then  able  to  bear  from  750°  to  850°  with- 
out boiling,  and  will  resist  decomposition  up  to  a  dull  red  heat. 

Experience  is  the  best  guide  for  the  regulation  of  the  tempe- 
rature of  the  bath;  but  care  must  be  taken  not  to  allow  any 
sensible  variation.  The  contents  of  the  containing  vessels  acquire 
the  temperature  of  the  bath  in  an  hour,  provided  the  latter  has 
been  kept,  all  the  time,  at  a  fixed  temperature. 

For  heating  to  redness,  Liebig's  furnace,  Fig.  139,  or  Hoff- 
man's furnace,  Fig.  166,  must  be  used ;  but  it  will  be  necessary 
to  place  the  tubes  in  the  centre  of  a  larger  sheet-iron  tube,  so  as 
to  intercept  the  contact  of  the  flame  with  the  glass.  When  glass 
flasks  are  used  as  the  containing  vessels  they  should  be  sealed  by 
closing  the  mouth  over  a  blast  lamp;  but  as  these  vessels  are  not 
capable  of  resisting  a  pressure  of  more  than  three  or  four  atmo- 
spheres, tubes  are  preferable,  and  almost  exclusively  used.  The 
glass  material  of  which  they  are  made  should  be  very  refractory, 
free  from  lead,  and  insensible  to  the  action  of  chemical  agents. 
That  kind  of  tube  used  for  organic  analyses  will  be  very  suitable, 
provided  it  is  sufficiently  thick.  The  thickest  resist  the  tension 
of  water  (steam)  up  to  520°,  and  that  of  spirits  of  turpentine  as 
high  as  680°  F. ;  or,  in  other  words,  they  will  stand  a  pressure 
of  50  to  60  atmospheres. 

When  extreme  temperatures  are  required,  it  is  not  necessary 
to  resort  to  tubes  of  other  and  more  resistant  material  than  glass, 
for  those  of  the  latter  can  be  made  available  by  proper  manage- 
ment. To  this  end,  the  substances  to  be  acted  upon  are  inclosed 
in  a  tube  of  about  four-tenths  of  an  inch  in  diameter,  which,  in 
its  turn,  is  placed  in  an  outer  tube  containing  a  liquid  less  vola- 
tile than  those  in  the  inner  tube,  and  of  such  a  nature  as  will  not 
cause  the  explosion  of  the  enveloping  tube,  but  only  counteract, 
by  its  tension,  a  part  of  the  internal  pressure  of  the  inner  tube. 
Alcohol  and  ether  may  be  thus  heated  to  680°  by  using  essence 
of  turpentine  as  the  liquid  in  the  exterior  tube. 

In  preparing  the  tube,  the  end  should  be  closed  in  the  flame 
without  the  use  of  a  blowpipe ;  and  subsequently  annealed.  After 
cooling,  the  solid  reagent,  if  such  is  to  be  used,  must  then  be  intro- 
duced, and  the  other  end  carefully  drawn  out  to  a  point.  Great  care 
must  be  taken  in  this  manipulation  to  preserve,  in  the  different 
parts  of  the  tube,  the  original  proportion  of  internal  diameter  and 


HEATING  IN   CLOSE  VESSELS.  379 

thickness;  for  it  is  especially  upon  this  mutual  ratio,  and  not 
upon  the  absolute  thickness,  that  the  power  of  resistance  depends. 
When  the  tube  is  cool,  the  liquids  are  then  introduced,  and  the 
point  sealed  in  the  flame  of  the  lamp.  The  point  of  closure  must 
be  very  fine,  as  in  the  disengagement  of  gases  it  allows  the  open- 
ing of  tubes  without  explosion. 

If  the  action  of  the  air  is  to  be  avoided,  before  sealing  the 
tube,  the  latter  must  receive  an  atmosphere  of  carbonic  acid  or 
hydrogen,  and  this  is  furnished  from  a  generator,  Fig.  172,  the 
delivery-tube  of  which  connects  with  its  point.  After  letting  in  a 
continuous  current  for  8  or  10  minutes,  the  operation  is  com- 
pleted. 

The  quantity  of  liquid  to  be  introduced  into  the  tube  varies 
with  the  degree  of  heat  to  which  it  is  to  be  carried ;  they  may  be 
filled  to  two-thirds  their  capacity  with  liquids  which  are  to  be 
heated  from  650°  to  750°.  In  all  cases  they  are  set  perpendicu- 
larly in  the  bath,  and  so  as  to  be  entirely  covered  by  the  oil. 

Tubes  which  are  to  be  heated  to  redness  must  have  a  length  of  20 
to  24  inches ;  and  the  charge  of  liquid  introduced  into  them  may 
be  1  to  1J  per  cent,  of  their  capacity.  When  gases  are  to  be 
subjected  to  treatment,  the  tube  is  drawn  out,  so  as  to  present  a 
very  slender  neck,  with  a  funnel-shaped  mouth,  filled  over  mer- 
cury, and  dexterously  sealed  at  the  neck  by  drawing  off  the  fun- 
nel-mouth over  the  lamp. 

When  the  tube  has  been  sufficiently  heated,  it  is  to  be  taken 
from  the  bath  and  opened,  but  as  it  may  contain  gases  in  such  a 
quantity  and  under  such  a  pressure  as  may  produce  explosion 
upon  the  least  shock,  great  care  is  necessary  to  prevent  accidents. 

If  the  generation  of  a  permanent  gas,  during  the  reaction,  is 
anticipated,  the  tube  must  be  inclosed  in  several  successive  enve- 
lops of  sheet-iron,  and  so  secured  at  both  ends  that  only  the  tip 
of  the  drawn-out  end  shall  project.  After  the  heating,  and  when 
the  bath  is  cooled  completely,  the  screw-nut  is  removed  from  the 
iron  tube,  and  the  latter  slightly  inclined,  so  as  to  allow  the  glass 
tube  to  fall  out  gently  upon  a  cloth. 

If  it  is  not  desired  to  study  the  gaseous  products  of  the  ope- 
ration, the  tube  is  then  wrapped  around  with  three  or  four  folds 
of  the  towel,  so  as  to  leave  only  the  point  projecting,  which  is 
then  clipped  off  with  a  pair  of  pincers.  If  the  effervescence 


380  LUTES. 

produced  by  the  disengaged  gas  is  excessive,  and  causes  loss  of 
liquid,  then  the  lower  end  may  be  broken  over  a  beaker  glass. 

In  certain  cases,  it  is  necessary  that  this  manipulation  should 
be  practised  at  a  little  distance  to  avoid  personal  injury;  for 
example,  in  heating  to  redness  tubes  containing  one-fifth  their 
volume  of  hydrochloric  ether  in  contact  with  hydriodate  of  am- 
monia, the  resulting  gases  are  sometimes  so  abundant  that  it  is 
impossible  to  open  the  tube  without  explosion,  and  in  such  case, 
if  the  solid  products  are  the  only  ones  required,  then  the  tube 
may  be  wrapped  completely  up  in  a  cloth  and  thrown  on  the 
floor.  The  solid  bodies  will  be  found  in  the  cloth  mixed  with  the 
fragments  of  glass.  , 

If  the  gases  are  the  required  products,  then  the  tube  must  be 
quickly  passed  up  into  an  inverted  receiver  or  tube,  filled  with 
mercury,  and  its  point  broken  against  the  interior  of  the  top. 
The  receiver  should  be  held  at  an  inclination  of  thirty  degrees, 
and  in  such  a  manner  as  to  protect  the  person  in  case  of  explo- 
sion. For  greater  safety,  it  is  advisable  to  envelop  the  receiver 
in  a  sheet-iron  casing. 

The  disengaged  gases  should  be  studied  immediately,  as  they 
may,  in  some  instances,  undergo  rapid  changes  over  mercury,  by 
the  loss  of  one  or  more  of  their  components.  As  an  instance, 
Berthelot  observes,  that  a  mixture  of  hydrogen  and  carbonic  acid 
lost  all  of  the  hydrogen,  even  with  two  intervening  fluid  strata, 
one  of  spirits  of  turpentine  of  four-tenths  of  an  inch  thickness, 
and  the  other  of  mercury  fifteen  times  as  deep. 


CHAPTER  XVIII. 

LUTES. 

IN  all  combinations  of  two  or  more  pieces  of  apparatus  or 
parts  of  them,  there  is  a  necessity,  in  chemical  operations  gene- 
rally, of  some  means  of  hermetically  closing  the  interstices  of 
their  joints  so  as  to  protect  the  inclosure  from  all  outward  com- 
munication. This  is  particularly  requisite  in  SUBLIMATION,  DIS- 
TILLATION, and  other  heating  operations,  and  indeed  in  all  expe- 


CAOUTCHOUC,  BLADDER,  FLAXSBED  LUTES.       381 

riments  with  gases  and  liquids,  wherever  it  is  desired  to  confine 
the  volatilized  particles  within  the  vessels  and  to  prevent  their 
escape  into  the  atmosphere  and  consequent  loss. 

To  accomplish  these  ends  we  make  use  of  lutes,  which  must 
vary  in  composition  and  mode  of  application  with  the  material 
and  construction  of  the  apparatus,  the  temperature  at  which  it  is 
to  be  heated,  and  the  nature  of  the  generated  products. 

Caoutchouc. — This  substance,  in  sheets,  is  particularly  useful 
for  forming  flexible  tubes  by  which  joints  may  not  only  be  ren- 
dered hermetical  but  also  flexible.  For  delicate  apparatus  it  is 
particularly  applicable  even  at  high  temperatures.  The  tubes  are 
made  as  directed  at  p.  304,  and  tied  above  and  below  the  joint 
as  at  x,  Fig.  218.  Sometimes  india-rubber  is  replaced  by  mus- 
lin, payed  over  after  its  adjustment  around  the  joints  with  a 
paste  made  by  the  mixture  of  caoutchouc  and  spirits  of  tur- 
pentine. 

Bladder. — Bladder  well  cleansed  and  divided  into  strips  an- 
swers very  well  to  a  limited  extent.  For  example,  when  moist- 
ened and  coated  with  white  of  egg  or  solution  of  bone-glue  or  of 
isinglass,  it  forms  an  excellent  covering  for  the  joints  of  retorts, 
tubes,  and  the  like,  to  the  surfaces  of  which  it  adheres  tenaciously. 
When,  however,  the  contained  ingredients  generate  corrosive 
vapors,  and  so  rapidly  as  to  strain  the  apparatus,  the  bladder  is 
unserviceable. 

Flaxseed  Lute. — Flaxseed  meal  mixed  to  the  consistence  of  a 
paste  with  water,  milk,  lime-water,  or  starch  paste.  This  lute  is 
very  manageable  and  impermeable,  but  does  not  withstand  a  heat 
greater  than  about  500°. 

If  just  the  sufficient  quantity  of  water  be  added  to  quicklime 
to  reduce  it  to  a  dry  powder,  and  the  two  mixed  well  and  rapidly 
with  white  of  egg  diluted  with  its  own  volume  of  water,  and  the 
mixture  spread  immediately  upon  strips  of  linen  and  applied  to 
the  part,  which  is  then  sprinkled  with  quicklime,  a  good  cement 
is  made.  Instead  of  white  of  egg,  lime  and  cheese  may  be  used, 
or  lime  with  weak  glue-water  or  blood.  This  lute  dries  very 
rapidly,  becoming  very  hard,  and  adhering  strongly  to  the  glass, 
but  its  great  inconvenience  is  the  want  of  flexibility. 

In  spirituous  distillations,  the  joints  of  the  apparatus  may  be 
closed  very  readily  and  effectually  by  a  stiff  paste  of  equal 


382  LIME,    PLASTIC,    RESINOUS   LUTES. 

weights  of  whiting  and  flaxseed  meal,  mixed  with  water.  We 
Lave  found  this  lute  invaluable  notwithstanding  its  want  of  flexi- 
bility. It  is  the  most  easily  made  and  most  cleanly  of  all  lutes, 
and  when  the  pressure  of  the  contained  vapor,  is  considerable,  it 
can  be  covered  with  strips  of  bladder  soaked  in  solution  of  bone- 
glue,  which  will  prevent  all  leakage. 

Lime  and  Bone-G-lue. —  Freshly  slacked  lime  made  into  a 
thick  paste  with  a  strong  solution  of  bone-glue,  makes  an  adhe- 
sive lute  very  applicable  for  closing  the  joints  of  vessels  which 
are  to  be  subjected  to  high  heats ;  as,  for  example,  those  in  which 
the  distillation  of  lime  and  sal  ammoniac  is  conducted  for  the 
production  of  gaseous  ammonia. 

Plaster  of  Paris. — Calcined  gypsum  made  into  a  paste  with 
glue  or  starch  water,  answers  the  same  purposes  as  the  above. 
When  covered  with  strips  of  bladder  it  is  rendered  entirely  im- 
permeable by  gases.  A  coating  of  oil  or  of  a  mixture  of  oil  and 
wax  has  the  same  effect  as  the  bladder,  and  the  lute  will  then 
stand  a  dull  red  heat. 

Plastic  lute  is  made  by  dissolving  melted  caoutchouc  in  hot 
linseed  oil,  adding  finely  powdered  pipe-clay  and  kneading  the 
whole  together  into  a  homogeneous  mass.  The  longer  it  is 
kneaded  the  better  is  its  quality,  and  to  prevent  its  hardening 
the  caoutchouc  should  not  be  in  deficient  proportion.  If  it  should 
become  hard  by  keeping,  it  may  be  softened  by  kneading  with  a 
little  spirits  of  turpentine. 

This  lute  closes  the  joints  without  hardening,  and  can  be  re- 
moved at  any  time  during  the  operation,  to  allow  a  change  in  the 
position  of  the  parts  of  the  apparatus. 

For  the  distillation  of  acids  or  other  corrosive  vapors,  it  is  very 
applicable. 

Soft  cement  is  prepared  by  fusing  yellow  wax  with  half  its 
weight  of  crude  turpentine  and  a  little  Venetian  red,  in  order  to 
color  it.  It  is  very  flexible,,  and  takes  any  desired  form  under 
the  pressure  of  the  fingers.  It  is  extremely  useful  at  common 
temperatures  for  tightening  tubes  in  cork,  and  as  a  coating  for 
rendering  corks  impermeable  to  gases. 

Resinous,  or  hard  cement,  is  made  by  fusing  together  at  the 
lowest  possible  temperature,  1  part  of  yellow  wax  and  5  or  6  of 
resin,  and  then  adding  gradually  1  part  of  red  ochre,  or  finely 


IRON   AND   FIRE   LUTES.  383 

powdered  brickdust  (plaster  of  Paris  succeeds  very  well),  and 
then  raising  the  temperature  to  212°  at  least,  until  no  more 
froth  arises,  or  agitation  takes  place,  and  stirring  it  continually 
until  cold.  This  cement  is  employed  in  a  hot  state,  and  is  very 
much  used  for  fixing  brass  caps,  &c.,  to  air-jars,  and  as  an  im- 
permeable coating  for  the  interior  of  wooden  vessels. 

Lute  for  joining  Glass  and  Steel — A  saturated  solution  of 
mastic  in  alcohol,  mixed  with  a  solution  of  isinglass  in  dilute 
spirits,  to  which  is  added  a  small  portion  of  galbanum  or  ammo- 
niac, is  an  excellent  cement  for  joining  glass  to  glass,  or  glass  to 
steel.  The  mixture  must  be  kept  in  a  well-stopped  bottle,  and 
be  always  warmed  previous  to  use. 

Lute  for  joining  Crucibles. — A  mixture  of  fine  clay  and  ground 
bricks  kneaded  into  a  paste  with  water,  holding  in  solution  one- 
tenth  of  borax,  answers  admirably  for  luting  the  joints  of  super- 
posed crucibles.  An  excellent  lute  for  this  purpose  and  also  for 
metallic  subliming  vessels,  is  finely  powdered  Stourbridge  clay, 
containing  a  little  sal  enixum,  and  made  into  a  stiff  paste  with 
water. 

Iron  Cement. — This  mixture  is  used  for  making  permanent 
joints  generally  between  surfaces  of  iron.  Clean  iron  borings  or 
turnings  are  to  be  slightly  pounded  so  as  to  be  broken,  but  not 
pulverized ;  the  result  is  to  be  sifted  coarsely,  mixed  with  pow- 
dered sal  ammoniac  and  sulphur,  and  enough  water  to  moisten 
the  whole  slightly.  The  proportions  are,  1  sulphur,  2  sal  ammo- 
niac, and  80  iron.  No  more  should  be  mixed  than  can  be  used 
at  one  time. 

lire  Lute. — The  best  fire  lute  is  that  employed  by  Mr.  Parker, 
and  is  composed  of  good  clay  2  parts,  sharp  washed  sand  8  parts, 
horse-dung  1  part.  These  materials  are  to  be  intimately  mixed ; 
and  afterwards  the  whole  is  to  be  thoroughly  tempered,  like 
mortar.  Mr.  Watt's  fire  lute  is  an  excellent  one,  but  is  more 
expensive.  It  is  made  of  finely  powdered  Cornish  (porcelain) 
clay,  mixed  to  the  consistence  of  thick  paint,  with  a  solution  of 
borax,  in  the  proportion  of  two  ounces  of  borax  to  a  pint  of  hot 
water. 

Fat  lute  is  prepared  by  mixing  dry  clay,  in  a  fine  powder,  with 
drying  oil,  so  that  the  mixture  may  form  a  ductile  paste.  It 
should  be  kept  under  cover,  preferably  in  a  greased  bladder. 


384  LUTE  FOR   COATING   FIRE  VESSELS. 

When  this  paste  is  used,  the  part  to  which  it  is  applied  ought  to 
be  very  clean  and  dry,  otherwise  it  will  not  adhere.  This  lute  is 
adhesive,  and  stands  a  pretty  high  heat,  but  requires  to  be  fast- 
ened down  with  strips  of  bladder.  Its  greatest  disadvantage  is 
the  difficulty  of  stopping  holes  which  may  be  blown  through  it  by 
escaping  vapor. 

Lead  and  Oil  Lute. — Red  lead  mixed  with  boiled  linseed  oil 
is  excellent  for  sealing  the  joints  of  steam- vessels.  It  hardens 
readily  and  bears  a  high  heat. 

Lute  for  coating  Fire  Vessels. — Faraday  gives  the  following 
directions  for  luting  iron,  glass,  or  earthenware  retorts,  tubes,  &c., 
for  furnace  operations.     When  the  lute  has  to  withstand  a  very 
high  temperature,  it  should  consist  of  the  best  Stourbridge  clay, 
which  is  to  be  made  into  a  paste,  varying  in  thickness  according 
to  the  judgment  of  the  operator.    The  paste  should  be  beaten  until 
it  is  perfectly  ductile  and  uniform,  and  a  portion  should  then  be 
flattened  out  into  a  cake  of  the  required  thickness,  and  of  such  a 
size  as  shall  be  most  manageable  with  the  vessel  to  be  coated. 
If  the  vessel  be  a  retort  or  flask,  it  should  be  placed  in  the  middle 
of  the  cake,  and  the  edges  of  the  latter  raised  on  all  sides,  and 
gradually  moulded  and  applied  to  the  glass ;  if  it  be  a  tube,  it 
should  be  laid  on  one  edge  of  the  plate,  and  then  applied  by  roll- 
ing the  tube  forward.  In  all  cases,  the  surface  to  be  coated  should 
be  rubbed  over  with  a  piece  of  the  lute  dipped  in  water,  for  the 
purpose  of  slightly  moistening  and  leaving  a  little  of  the  earth 
upon  it ;  if  any  part  of  the  surface  becomes  dry  before  the  lute 
is  applied,  it  should  be  re-moistened.     The  lute  should  be  pressed 
and  rubbed  down  upon  the  glass,  successively  from  the  part  where 
the  contact  was  first  made  to  the  edges,  until  all  air  bubbles  are 
excluded,  and  an  intimate  adhesion  effected.     When  one  cake  of 
lute  has  been  applied,  and  is  not  large  enough  to  cover  the  whole 
required  surface,  another  must  be  adapted  in  a  similar  manner. 
Great  care  must  be  taken  in  joining  the  edges,  for  which  purpose 
it  is  better  to  make  them  thin  by  pressure,  and  also  somewhat 
irregular  in  form,  and  if  at  all  dry,  they  should  be  moistened  with 
a  little  soft  lute.     The  general  thickness  may  be  about  one-quar- 
ter to  one-third  of  an  inch. 

Being  thus  luted,  the  vessels  are  afterwards  to  be  placed  in 
a  warm  situation,  over  the  sand-bath  or  near  the  ash-pit,  or  in 


MODE   OF  APPLYING    LUTES.  385 

the  sun's  rays.  They  should  not  be  allowed  to  dry  rapidly  or 
irregularly,  and  should  be  moved  now  and  then  to  change  their 
positions. 

To  prevent  cracking  during  desiccation,  and  the  consequent 
separation  of  the  coat  from  the  vessel,  some  chemists  recommend 
the  introduction  of  fibrous  substances  into  the  lute,  so  as  mecha- 
nically to  increase  the  tenacity  of  its  parts.  Horse-dung,  chopped 
hay  and  straw,  horse  and  cow  hair,  and  tow  cut  short,  are  amongst 
the  number.  When  they  are  used,  they  should  be  added  in  small 
quantity,  and  it  is  generally  necessary  to  add  more  water  than 
with  simple  lute,  and  employ  more  labor  to  insure  a  uniform 
mixture.  It  is  best  to  mix  the  chopped  material  with  the  clay 
before  the  water  is  put  to  it,  and  upon  adding  the  latter,  to  effect 
the  mixture,  at  first  by  stirring  up  the  mass  lightly  with  a  pointed 
stick  or  fork ;  it  will  then  be  found  easy,  by  a  little  management, 
to  obtain  a  good  mixture  without  making  it  very  moist. 

The  luting  ought  to  be  made  as  dry  as  possible,  consistent  with 
facility  in  working  it.  The  more  wet  it  is,  the  more  liable  to 
crack  in  drying,  and  vice  versd. 

Mr.  Willis  recommends,  when  earthenware  retorts,  &c.,  are  to 
be  rendered  impervious  to  air,  the  following  coating.  One  ounce 
of  borax  is  to  be  dissolved  in  half  a  pint  of  boiling  water,  and 
as  much  slacked  lime  added  as  will  make  a  thin  paste.  This 
composition  is  to  be  spread  over  the  vessel  with  a  brush,  and 
when  dry,  a  coating  of  slacked  lime  and  linseed  oil  is  to  be  ap- 
plied. This  will  dry  sufficiently  in  a  day  or  two,  and  is  then  fit 
for  use. 

Cement  for  Labels. — Gum  tragacanth  boiled  with  hot  water 
makes  the  most  adhesive  paste  for  securing  labels  upon  glass  or 
other  smooth  surfaces.  The  addition  of  a  few  drops  of  acetic 
acid  retards  its  decomposition  and  keeps  it  unaltered  for  a  long 
time.  By  moistening  the  labels  with  a  very  weak  alcoholic  solu- 
tion of  corrosive  sublimate,  before  pasting  them  on  the  bottles, 
they  are  rendered  proof  against  the  obliterating  action  of  mould 
and  dampness. 

Mode  of  applying  Lutes.— Lutes  are  applied  whilst  soft,  being 
adjusted  to  the  joints  by  the  hand.  As  they  become  dry,  occa- 
sional compression  by  the  fingers  is  necessary  to  render  them 
compact.  So  also  when  any  leaks  occur  they  must  be  closed 

25 


386  THE   BAROMETER. 

•with  fresh  portions  of  lute  smeared  over  and  pressed  in  by  the 
end  of  the  thumb.  When  bladder  or  muslin  is  to  be  pasted  over 
lute,  the  joint  made  with  the  latter  must  first  have  dried. 

When  the  operation  is  finished,  and  the  apparatus  is  to  be  dis- 
connected, the  lute  must  be  removed  first  with  the  hands.  If,  as 
is  often  the  case  in  the  use  of  hard  lutes  in  fire  processes,  they 
adhere  tenaciously,  then  the  use  of  a  knife,  or  when  the  vessels 
are  metallic,  a  chisel  becomes  necessary. 


CHAPTER  XIX. 

THE   BAROMETER. 

THE  Barometer,  so  important  in  its  discovery  as  marking  a 
great  epoch  in  the  history  of  science,  has  not  become  less  so  in 
its  subsequent  varied  applications  as  an  indispensable  instrument 
for  physical  research.     Not  to  speak  here  of  its  use  in  meteo- 
rology for  indicating  the  changes  that  are  occurring,  periodically 
or  irregularly,  in  the  weight  of  our  atmosphere,  or  of  its  employ- 
ment in  geography  for  determining  expeditiously  and  with  rea- 
sonable accuracy  differences  of  level  between  different  points  of 
the  earth's  surface,  the  demand  for  its  appliance  in  the  labora- 
tory is  almost  ceaseless.     Not  a  weighing  can  be  made,  at  least 
where  the  aim  is  minute  precision,  of  solid  bodies,  without  its  ob- 
servation, unless  (what  is  rarely  the  case)  the  object  to  be  weighed 
and  the  weights  themselves  are  of  the  same  material,  or  have  the 
same  specific  gravity;   while   in  the  measurement  of  gaseous 
bodies,  whose  volume,  at  any  moment,  evidently  is  regulated  by 
the  pressure  of  the  atmospheric  medium  which  circumscribes 
them,jts  readings  have  to  be  continually  combined  with  what- 
ever other  observations  that  have  been  made,  in  order  to  educe 
the  proper  arithmetical  result. 

With  such  frequency  of  necessary  and  varied  appliance,  there 
might  be  expected  (as  is  in  fact  realized)  a  corresponding  variety 
in  the  arrangements,  both  formal  and  substantial,  of  the  instru- 
ment itself;  all  subject,  however,  to  one  essential  condition,  viz., 
the  establishment  and  maintenance  of  a  perfect  vacuum  in  some 
part  of  the  apparatus.  Besides  this  indispensable  condition  there 


WHEEL-BAROMETER.  387 

are  others,  too,  of  greater  or  less  generality,  which  have  also  to 
be  considered ;  such  as  the  precision  with  which  the  zero  of  the 
scale  can  be  ascertained,  the  permanence  of  such  zero,  the  sym- 
pathy between  the  scale  itself  and  the  material  movement  in  the 
apparatus  which  it  is  intended  to  measure,  the  openness  of  said 
scale,  or  the  minuteness  with  which  its  readings  can  be  made,  &c. 
There  will  be  occasion  to  indicate  these  conditions  more  expressly 
in  the  account,  which  is  of  sufficient  interest  to  be  given  here, 
briefly,  of  the  main  modifications  which  the  instrument  has  suc- 
cessively and  at  divers  times  undergone. 

All  these  modifications  may,  for  convenience  in  description,  be 
grouped  into  two  divisions  consisting,  1st,  of  Stationary  Baro- 
meters ;  and,  2d,  of  Barometers  which  are  intended  to  be  port- 
able. These  last,  because  of  the  geographical  use  which  stimu- 
lated their  device,  are  ordinarily  termed  Twowntaw-barometers ; 
and  by  the  former  are  meant  such  as  not  being  devised  for 
transportation  require  a  special  caution  in  being  moved  from 
place  to  place,  and  a  treatment  afterwards  more  or  less  equiva- 
lent to  the  pains  which  were  requisite  in  their  being  first  set  up. 
In  other  respects,  as,  for  instance,  in  regard  to  the  conditions 
which  have  been  just  spoken  of,  there  is  no  generic  difference 
between  them,  only  that  while  the  mountain-barometers  can  fulfil 
at  all  times  the  functions  of  the  stationary  ones,  the  converse 
does  not  hold  good.  Hence,  except  for  purposes  of  ornament  or 
amusement,  and  for  aims  which  may  be  called  extra-technical, 
stationary  barometers  are  now  rarely  constructed.  But  whenever 
or  however  constructed,  they  consist  essentially  of  a  glass  tube, 
closed  at  one  end,  set  vertically,  with  the  closed  end  uppermost, 
and  containing  some  fluid  mercury,  sulphuric  acid,  water,  &c., 
the  height  of  the  column  of  which  will  be,  of  course,  inversely 
as  its  specific  gravity,  in  order  to  be  in  equilibrium  with  the  pres- 
sure of  the  atmosphere ;  and  their  distinctive  characteristic  is  the 
permanent  aperture  of  the  lower  end  of  the  tube,  and  the  direct 
contact  of  the  fluid  column  there  with  the  external  air. 

Of  this  class  the  wheel-barometer  may  serve  as  a  type. 

Wheel-Barometer.— -This  is  the  instrument  most  generally  pro- 
cured when  the  object  is  to  have  an  amusing  weather-glass ;  and 
its  construction  can  be  readily  understood  from  the  adjoining 
sketch,  Fig.  325,  in  which  the  dotted  lines  show  the  tube  turned 


888  WHEEL-BAROMETER. 

up  into  a  short  syphon,  through  whose  permanent  aperture  a  float 

enters  and  rests  on  the  mercury  sur- 
face, counterpoised  so  as  to  yield  to  or 
follow  that  surface,  by  a  weight  the 
connecting-string  of  which  passes  over 
a  pulley,  as  seen  also  in  dotted  lines. 
The  arbor  of  this  pulley  passes  hori- 
zontally to  the  outside  of  the  casing, 
and  there  is  fitted  with  an  index  as 
shown,  which  index  revolves  to  the 
left  hand  or  to  the  right,  according  as 
the  surface  of  the  mercury  in  the 
syphon  rises  or  falls,  and  points  out 
on  the  graduated  circle  around  it  the 
proportionate  extent  of  such  rise  or  fall.  As  the  aggregate 
weight  of  the  float  and  counterpoise  is  very  small,  and  might  not 
create  friction  enough  to  prevent  the  string  connecting  them  from 
slipping  on  the  pulley,  it  is  usual  to  sever  said  string,  and  attach 
its  ends  to  the  pulley,  which  is  turned  with  a  double  groove.  The 
diameter  of  this  pulley  is  most  conveniently  made  such  that  a 
half  revolution  shall  correspond  to  the  range  that  is  exhibited  on 
the  dial.  When  the  range  takes  in  the  whole  circumference  of 
the  dial-plate,  of  course  a  whole  revolution  of  the  pulley  becomes 
necessary,  and  the  string  is  better  unsevered.  It  is  plain  that  in 
this  arrangement  of  two  columns,  the  vertical  movement  of  either 
is  but  half  of  what  it  would  be  in  a  single  one ;  and  in  so  far  the 
scale,  were  it  a  vertical  one,  would  be  only  half  as  serviceable ; 
but  this  can  be  counteracted  to  any  extent,  and  is  so  in  a  greatly 
multiplied  proportion  by  the  reading  being  circumferential. 
Wheel-work  is  sometimes  attached  to  the  pulley-arbor,  by  which 
minute  readings  can  be  made  still  more  sensible. 

But,  with  all  this,  the  friction  of  the  apparatus,  and  the  diffi- 
culty of  boiling  the  mercury  in  the  tube,  without  which  ebullition, 
the  freedom  of  the  column  from  air  and  the  perfection  of  the 
vacuum  above  can  never  be  obtained,  have  consigned  this  form  to 
uses  where  accuracy  is  not  aimed  at,  and  for  a  laboratory  imple- 
ment it  is  altogether  unsuitable. 

Barometers  of  the  other  kind,  whose  unsealed  extremity  yet 
admits  of  being  cut  off  at  discretion  from  connection  with  the  ex- 


NEWMAN'S  BAROMETER.  389 

ternal  air,  may  be  divided  into  two  classes,  viz.,  cistern  and 
syphon  barometers.  In  the  first,  the  original  single  tube,  which 
with  Toricelli  or  Pascal  plunged  its  open  extremity  into  a  wide 
cup  or  bowl  of  quicksilver,  has  its  own  cup  or  cistern  permanently 
attached  to  it,  protected  from  fracture  by  suitable  precautions  to 
support  and  strengthen  it. 

Newmans  Barometer. — In  some  kinds,  as  in  the  barometer  of 
Newman,  the  cistern  is  made  of  iron,  and  the  passage  for  air, 
from  the  outside  to  the  inside,  is  effected  by  means  of  a  screw- 
plug,  which  is  removable  at  pleasure.  When  this  is  open,  the 
pressure  maintains  the  mercurial  column  at  a  corresponding 
height,  which  is  read  off  with  the  aid  of  a  vernier  from  the  en- 
closing brass  tube  ;  if  this  pressure  increases  the  column  rises ;  if 
it  diminishes  the  column  falls.  In  either  case,  it  is  clear  that  the 
displacements  in  the  tube  correspond  to  inversely  proportionate 
displacements  in  the  cistern,  by  which  the  level  of  the  fluid  there 
is  raised  or  depressed ;  by  which  it  differs  from  what  was  assumed 
in  the  laying  off  of  the  scale  as  its  starting-point  or  normal-zero, 
and  by  which  there  is,  to  the  extent  of  difference  in  question,  an 
error  in  the  apparent  height  of  the  column.  As  this  normal-zero 
mark,  as  well  as  the  mercury  surface  in  the  cistern,  are  no  longer 
visible  after  the  instrument  has  been  put  together,  the  correction 
of  this  error  has  to  be  found  in  a  previous  comparison  made  by 
the  maker,  and  furnished  with  or  recorded  on  the  instrument,  of 
the  relative  capacities  of  the  tube  and  of  the  cistern.  If  the  tube 
and  cistern  were  alike  perfectly  cylindrical,  it  would  be  sufficient 
for  ascertaining  this  correction  to  know  their  diameters  respec- 
tively, to  the  squares  of  which  the  displacements  would  be  in- 
versely proportionate.  Thus,  if  the  tube  was  0-25  inch  bore, 
and  the  cistern  2-5  inches  diameter,  or  10  times  as  great,  then 
a  fall  of  1  inch  in  the  tube  would  be  compensated  by  a  rise  of 
0-01  inch  in  the  cistern,  or,  in  general,  the  rise  in  the  cistern 
would  be  T  $5  of  the  fall  in  the  tube,  and  vice  versd.  But,  as  this 
regularity  of  shape  is  rarely  or  never  existing,  the  usual  mode  is 
to  fill  the  entire  tube,  or  a  known  length  of  it,  with  mercury,  and 
then  extravasating  it  into  the  cistern,  to  measure  the  difference 
of  level  which  has  been  produced  by  the  addition.  So,  if  30 
inches  length  of  tube  is  found  to  contain  a  quantity  of  mercury 
enough  to  raise,  when  poured  into  the  cistern,  the  previous  sur- 


390  NEWMAN'S  BAROMETER. 

face  by  0-3  inches,  the  technical  correction  for  capacity  of  cistern 
is  T^  (as  before)  of  the  difference  between  any  actual  reading 
and  the  reading  of  the  column  originally,  when,  in  the  construc- 
tion of  the  instrument,  the  zero  of  the  scale  was  adjusted  to  the 
surface  of  the  mercury  in  the  cistern.  This  last-named  reading 
is  by  artists  called  the  neutral  point,  and  is  stated  along  with 
the  correction  for  capacity.  It  follows  from  the  very  epithet 
neutral,  as  well  as  from  what  has  been  said  just  now,  that  the 
application  of  the  capacity-correction,  i.  e.  whether  additively  or 
subtractively,  depends  upon  which  side  of  the  neutral  point  the 
surface  in  the  cistern,  at  the  epoch  of  the  actual  reading,  may 
happen  to  be,  t.  e.  whether  above  or  below.  If  the  actual  read- 
ing is  greater  than  that  for  the  neutral  point,  then  the  cistern- 
surface  must  be  below  said  point,  and  the  correction  for  capacity 
is  additive,  and  vice  versd. 

Thus,  for  example,  the  correction  for  cistern- capacity  in  a 
given  case  was  47,  and  the  stand  of  the  neutral  point  was  30-180 
inches.  Upon  one  occasion  the  reading  of  the  column  was  found 
to  be  30-526  inches.  Of  course,  the  ascent  in  the  tube  had  been 
(30-526  —  30-180  =)  0-346  inch;  and  the  corresponding  depres- 
sion in  the  cistern  had  become  ( =)  0-008  inch,  which, 

because  of  its  sign,  is  additive,  and,  therefore  (30-526  +  0-008  =) 
30-534  is  the  reading  that  would  have  been  shown,  if,  by  any 
contrivance,  the  cistern-surface  could  have  been  maintained  at 
the  zero  of  the  scale.  So,  again,  with  the  same  barometer  oc- 
curred an  apparent  stand  of  29-742  inches,  showing  a  descent  in 
the  tube  of  (29-742  —  30-180  =)  —  0-438,  and  a  corresponding 

rise  in  the  cistern  of  — =  —  0-011  inch,  which,  because 

41 

of  its  sign,  is  subtractive,  and  the  true  reading  would  have  been 
(29-742  —  0-011  =)  29-731  inches,  could  the  zero  have  remained 
as  at  first.  -  ;*: 

The  cumbrousness  of  this  correction,  and  the  possibility  of 
error  from  confusing  the  signs,  and  adding  where  one  ought  to 
subtract,  or  vice  versd,  stimulated  devices  for  maintaining  the 
zero  so  as  to  dispense  with  the  necessity  of  any  correction.  The 
readiest  suggestion  was  to  make  the  bottom  of  the  cistern  mov- 
able, so  as  to  be  able  always  to  restore  the  surface  there  to  the 


TROUGHTON'S  BAROMETER. 


391 


Fig.  326. 


original  zero  from  which  the  graduation  started.  Of  course,  the 
surface  in  the  tube  would,  in  such  case,  undergo  an  equable  dis- 
placement, and  there  the  apparent  reading  became  normal  and 
true. 

One  of  the  modes  of  effecting  this  is  that  proposed  and  executed 
by  Mr.  Troughton  some  seventy  years  since,  and,  in  fact,  prece- 
ding by  nearly  half  that  period  the  iron  cisterned  barometers  of 
Newman,  which  have  been  just  now  spoken  of.  The  details  of 
Troughton's  arrangement  will  be  easily  understood  from  the  ad- 
joining sketch;  and  they  have  so  far  approved  themselves  in 
practice  as  to  be  substantially  and  with  but  slight  variations  in 
form  perpetuated  to  the  present  day  in  England  and  America. 

Troughton's  Barometer. — The  sketch  of  this  instrument,  Fig. 
326,  is  restricted  to  the  lower  part  of  the  apparatus,  and  is  in- 
tended to  show  within  a  glass  cylinder, 
of  about  2-5  inches  in  diameter,  and  as 
much  in  height,  whose  bottom  of  buck- 
skin, cemented  on  to  the  rim,  and  still 
farther  supported  there  by  a  brass  ring 
that  is  screwed  up  tight  by  the  outer 
brass  casing,  enables  it  to  hold  the  mer- 
cury. The  top  is  of  wood  or  iron,  also 
leathered,  through  which  the  tube  plunges 
into  the  mercury;  and  appropriate  shoul- 
der-pieces serve  both  to  steady  the  tube 
and  to  receive  and  bear  the  outside  brass 
cylinder  that  encompasses  and  protects 
the  tube.  The  cistern  thus  furnished  is 
enclosed  in  a  brass  cylinder,  in  the  base 
of  which  works  vertically  a  screw  termi- 
nated above  in  a  suitable  disk,  that  holds 
and  can  be  made  to  press  against  the  lea- 
ther bottom,  and  thus  enlarge  or  diminish 
the  capacity  of  the  cistern.  This  outside 
brass  cistern  cover  is  not  everywhere  continuous ;  but  about  one- 
fifth  of  the  height  from  the  top  has  two  opposite  horizontal  slits 
cut  in  it  about  0-25  inch  wide,  thus  allowing  one  to  see  through 
the  glass  the  surface  of  the  mercury,  and  the  stem  of  the  tube 
when  the  screw  is  lowered.  The  upper  edge  of  these  slits  is  the 


392  TROUGHTON'S  BAROMETER. 

zero  of  the  graduation  and  the  normal  level  of  the  surface  in  the 
cistern ;  and  to  this  edge,  the  eye  being  applied  at  the  same  level 
and  receiving  the  light  through  from  the  opposite  side,  the  sur- 
face of  the  mercury  is  lifted  by  working  the  screw  until  the  line 
of  light  thus  received  becomes  the  least  possible,  or  until  the 
slightest  further  turn  of  the  screw  would  shut  it  out  entirely. 
This  phenomenon  of  the  minimum  visibile,  or  the  least  line  of 
light,  is  the  test  of  the  zero  also  equally  when  the  mechanical 
adjustments  happen  to  be  made  in  the  contrary  direction,  and 
the  screw  to  be  lowered  instead  of  raised. 

As  to  the  upper  part  of  the  Troughton  barometer,  it  may  be 
said  that  the  glass  tube  is  sheltered  by  a  brass  one  rather  larger 
than  itself;  which  brass  tube  is  continuous  for  about  half  the 
height,  and  for  the  remainder  is  slotted  on  both  sides  opposite, 
so  as  to  expose  to  view  the  mercurial  column  and  the  tube  to  near 
its  very  top.  On  one  edge  of  one  of  these  slots  the  graduation 
is  made,  its  zero  being  the  edge  of  the  slit  in  the  cistern  before- 
mentioned,  its  actual  division  commencing  at  about  15  inches,  being 
continued  generally  up  to  31  inches,  and  its  subdivisions  capable 
of  being  read  to  ^\Q  or  sometimes  y^^  of  an  inch,  by  means  of 
a  vernier,  which  is  inscribed  on  a  smaller  brass  tube  that  moves 
inside  of  the  slotted  one,  and  is  so  rebutted  as  to  present  the 
vernier  always  to  the  graduation.  The  motion  of  this  sliding- 
tube,  through  spaces  of  one-tenth  of  an  inch  and  upwards,  is  by 
hand ;  its  smaller  motions  are  regulated  by  a  screw  which  works 
vertically  downwards  in  the  very  top  of  the  brass  casing,  and  by 
means  of  which  the  lower  edge  of  the  sliding-tube  can  be  brought 
into  optical  contact  with  the  meniscus  or  upper  convex  surface  of 
the  mercury  in  the  tube.  This  contact  is  effected  in  the  same 
way  as  that  practised  for  the  adjustment  of  zero,  viz.,  the  screw- 
ing down  until  the  line  of  light  between  the  mercury-surface, 
which  coincides  with  the  beginning  of  the  vernier  and  the  sliding- 
edge,  is  the  least  possible. 

"When  the  instrument  is  intended  to  be  transported  from  place 
to  place,  the  function  of  the  lower  screw  is  then  to  force  the  column 
up  to  the  top  of  the  tube,  which  is  ordinarily  visible,  or  rather 
in  order  to  avoid  all  strain  and  consequent  fracture  very  near  to 
the  ton.  The  sharp  click  that  is  made  when  after  such  screwing 


TROUGHTON'S  BAROMETER.  393 

up  is  done,  the  instrument  is  reversed,  and  the  cistern  held  upper- 
most, is  evidence  that  the  column  is  not  unduly  pressed. 

This  method  of  reading  by  an  adjustable  surface  from  a  per- 
manent and  visible  zero,  has,  from  its  facility  and  real  merit, 
obtained  wide  acceptation  ;  and  many  instruments  are  made  which 
have  this  feature,  though  very  few  other  of  the  Troughton  ar- 
rangement. In  those,  the  cistern  is  ordinarily  made  of  wood  into 
the  long  slits  or  windows,  in  whose  sides  narrow  pieces  of  glass 
are  cemented  to  allow  the  transmission  of  light ;  the  bottom  is  of 
leather  as  before ;  the  screw  works  in  the  same  manner ;  the  zero 
of  the  scale  is  defined  by  the  edges  of  the  slit  in  the  enclosing 
brass  case  similarly.  But  the  case  to  protect  the  tube  is  wood ; 
and  the  scale  is  a  flat  slip  of  brass  fastened  against  the  jamb, 
which  is  produced  by  cutting  away,  for  a  height  of  twelve  or 
fifteen  inches  from  the  top,  about  the  third  part  of  the  matter  of 
the  wooden  cylinder,  so  as  to  show  the  tube  on  one  side.  The 
reading  is  made  by  a  vernier  slide,  worked  by  hand  upon  the  slip 
aforesaid,  and  having  a  curved  lateral  index  that  embraces  a  part 
of  the  tube,  and  may  be  adjusted  to  the  meniscus  of  the  column. 
Tube,  and  slide,  and  hollow,  are  all  covered,  when  desirable,  by  a 
portion  of  brass  tubing, — nearly  a  semicircle  in  section, — which 
works  round  horizontally,  and  screens,  or  at  pleasure  reveals, 
what  is  within.  These  barometers  are  hung  by  a  ring  at  the  top 
of  the  wooden  case  to  some  convenient  support ;  while,  in  the 
Troughton  arrangement,  the  suspension  is  by  a  collar  and  trun- 
nions, placed  about  midway  of  the  length,  and  resting  in  gimbals 
that  are  set  in  the  head  of  the  tripod,  which,  when  the  instru- 
ment is  dismounted  and  reversed,  serves  for  its  packing-case. 

This  method  of  adjustment  to  zero,  however,  has  not  been  so 
favorably  received  by  the  Continental  artists,  who  prefer  the 
mode  adopted  by  Fortin.  In  this  the  glass  cistern  is  much  more 
revealed  than  in  the  Troughton  arrangement,  in  order  to  have 
illumination  enough  to  see  the  mercury-surface,  and  also  an  ivory 
point  which  projects  vertically  downwards  from  the  top  of  the 
cistern.  Otherwise,  the  arrangements  are  similar  to  what  has 
been  described ;  the  bag  is  screwed  up,  and  the  cistern  surface 
displaced,  until  the  direct  image  of  the  ivory  pointer  and  its 
image  reflected  from  the  mercury-surface  just  meet  apex  to 


394 


HASSLER  S    BAROMETER. 


Fig.  327. 


apex.  When  this  optical  contact  is  made,  the  ivory  point,  whose 
very  terminus  is  in  the  plane  of  the  zero  of  the  graduation,  just 
touches  without  piercing  the  mercury-surface,  and  the  scale  is 
properly  adjusted  to  be  read. 

Hasslers  Barometer. — Mr.  Hassler  devised,  some  twenty  years 
ago,  for  use  in  the  United  States  Coast  Survey,  something  quite 
different  from  all  the  types  that  have  been  indicated.  In  this, 
the  principal  parts,  the  tube  and  the  scale,  are  no  longer  attached 
but  separated,  and  the  cistern,  which  may 
be  any  convenient  vessel  that  will  hold 
mercury,  is  also  separate,  and  may  be  ap- 
plied, during  cessation  of  its  functions  here, 
to  various  other  uses  or  purposes  to  which 
it  may  be  fitted  or  convertible.  The  ad- 
joining sketch  of  the  suspensory  and  upper 
part  of  the  apparatus,  Fig.  327,  will  render 
the  following  brief  description  sufficiently 
intelligible.  The  tube  there  is  a  naked 
tube  containing  mercury.  At  its  upper 
end,  a  metallic  ferrule  embraces  it,  with  a 
curved  piece  of  wire  fastened  to  its  basket 
handlewise,  and  allowing  it  to  be  suspended 
on  a  hook.  To  the  lower  end  of  the  tube 
is  cemented  a  steel  ferrule,  with  two  pro- 
jecting prongs  or  arms  diametrically  oppo- 
site, over  which  slips,  through  guide-holes, 
a  steel  plate  having  a  leather  cushion  on 
one  side  of  the  diameter  to  fit  the  end  of 
the  tube.  When  this  plate  is  pushed  down, 
two  slots  in  the  arms  allow  a  key  or  wedge 
to  be  slipped  through,  the  pressure  of  which 
forces  the  plate  and  cushion  sufficiently 
home  to  retain  the  mercury.  This  plate  is 
so  pushed  home  and  keyed  when  the  tube  is  prepared  for  trans- 
portation ;  when  it  is  set  up  for  observation,  of  course,  the  key  is 
taken  out,  and  the  plate  removed.  The  scale  is  a  curved  slip  of 
brass,  ordinarily  divided  from  25  to  31  inches,  and  with  a  vernier 
that  reads  down  to  yj^  of  an  inch,  properly  fastened  to  a  light 
steel  rod,  whose  lower  end  is  the  zero  of  the  graduation,  and  is 


HASSLER'S  BAROMETER.  395 

intended  to  be  in  contact  with  the  cistern  surface.  The  upper 
end  of  the  rod  is  tapped  with  a  screw,  which  is  intended  to  pass 
through  an  oblong  hole  in  a  bracket,  as  seen  in  the  sketch,  and 
to  be  retained  on  the  other  side  by  a  nut.  Another  similar  hole 
in  the  same  bracket  is  for  a  hook  to  support  the  barometer-tube, 
which  hook  is  likewise  held  and  its  motion  regulated  by  a  nut 
above.  The  rectangularity  of  the  hole,  which  corresponds  to  a 
flattening  of  the  sides  of  the  screw,  is  intended  to  prevent  the 
turning  of  the  whole  apparatus  when  the  nut  is  worked.  At  the 
zero  end  of  the  steel  rod,  and  at  some  prescribed  distance  above 
the  very  zero  (in  fact,  0'5  inch),  a  mark  is  found  going  round 
the  rod ;  to  which  mark  it  is  intended,  by  working  the  nut  before 
spoken  of,  to  adjust  the  fiducial  edge  of  an  ivory  float  (of  exactly 
the  same  height  from  its  base  to  said  fiducial  edge  as  the  pre- 
scribed distance  aforesaid),  so  that  when  the  edge  and  the  mark 
correspond,  the  base  of  the  float  and  the  end  of  the  rod  are 
exactly  on  the  same  level,  both  in  contact  with  the  mercury-sur- 
face, and  said  surface,  therefore,  at  the  zero  of  the  scale. 

In  the  use  of  this  form  of  instrument,  supposing  it  just  taken 
out  of  its  packing-case,  and  with  the  open  end  outwards,  the  first 
thing  is  to  withdraw  the  key  that  holds  the  plate ;  then  to  remove 
the  plate ;  then  to  pour  a  little  clear  mercury  from  the  vessel  used 
as  the  cistern  (and  which  is  assumed  as  having  been  previously 
filled  from  the  travelling  flask  or  otherwise)  into  the  tube,  which 
is  held  a  little  inclined  from  the  perpendicular  at  first  in  order  to 
let  the  new  mercury  wash  off,  as  it  were,  any  oxide  or  amalgam 
that  may  have  been  formed,  and  which  washing  may  be  caught 
either  in  the  cistern  or  in  some  separate  vessel ;  then,  when  the 
tube  is  quite  full,  to  close  it  with  the  end  of  the  middle  finger  so 
as  to  prevent  the  escape  of  mercury,  and,  so  closed,  to  invert  the 
tube  and  plunge  its  end  in  the  cistern,  withdrawing  the  finger 
under  the  mercury  cautiously  so  as  to  moderate  the  descent  of 
the  column  in  the  tube.  Then  the  basket-handle  ring  is  sus- 
pended on  the  hook  before-mentioned,  and  the  tube  is  ready  to 
be  measured.  For  this  measurement,  the  scale  is  next  applied 
by  slipping  the  ivory  float  over  the  lower  end  of  the  steel  rod, 
passing  its  lapped  end  through  the  appropriate  opening  in  the 
bracket,  catching  it  there  with  the  nut,  and  working  the  nut  up 
or  down  until  the  mark  on  the  lower  end  corresponds  with  the 


396          ALEXANDER'S  BAROMETER. 

fiducial  edge  of  the  float.  The  distance  apart  of  the  holes  in  the 
bracket,  and  the  width  of  the  graduated  curved  plate,  are  such 
and  so  proportioned  that  when  the  tube  and  rod  have  been  fast- 
ened in  the  position  indicated,  the  curved  index  projecting,  as 
seen  from  the  vernier  plate,  embraces  without  touching  the  tube, 
and  can  be  readily  brought,  by  means  of  the  vernier-rack,  to  a 
due  coincidence  with  the  top  of  the  column,  and  the  reading  of 
the  scale  then  made.  When  the  instrument  is  to  be  taken  down, 
the  various  motions  that  have  been  described  have  to  be  made  in 
a  reversed  order.  For  ascertaining  the  temperature  of  the  mer- 
cury a  loose  thermometer  is  either  stood  in  the  cistern,  if  the 
sides  of  that  vessel  are  high  enough  to  retain  it,  or  is  hung  from 
the  bracket  by  a  suitable  string  or  wire  that  allows  it  to  plunge 
properly  into  the  cistern.  This  method  of  ascertaining  the  tem- 
perature is  a  normal  peculiarity  in  this  arrangement,  as  will  be 
spoken  of  more  particularly  presently  when  the  correction  for 
temperature  comes  to  be  discussed. 

Alexander's  Barometer. — The  same   mode  of  applying  the 
thermometer  is  found  in  another  arrangement  by  J.  H.  Alex- 
ander, which  presents  some  other  peculiarities  that  appear  to 
have  recommended  it  to  frequent  employment.     This,  like  the 
former,  consists  of  a  naked  tube,  whose  open 
Fig-  328.  en(^  terminated  with  a  slip  of  platinum  welded 

on  the  inside  for  a  purpose  that  will  be  pre- 
sently spoken  of  in  relation  to  deterioration 
of  barometers,  bears  also  a  sort  of  flat  cistern 
-|/  which  is  permanently  full  of  mercury,  and 

— 5jJJ"  which  is  shown  in  the  adjoining  Fig.  328. 
This  cistern  is  formed  as  follows : — First,  a 
collar  of  iron  is  cemented  on  the  outside  of  the  tube  near  its  ex- 
tremity, to  which  is  screwed  permanently  a  bell-shaped  dish  of 
iron  open  at  bottom.  The  bottom  is  then  closed  by  a  sheet 
of  Russia  iron  thinned  by  hammering  and  then  annealed  until  it 
has  become  extremely  flexible,  which  is  cut  round  to  fit  on  a 
rebate  within  the  dish,  and  is  then  firmly  held  there  by  a  ring 
of  iron  which  screws  inside  of  the  dish  and  up  to  the  rebate.  A 
hole  which  has  been  drilled  horizontally,  Fig.  329,  into  the  side 
of  the  dish,  is  closed  by  a  screw-plug,  which  admits  of  removal 
at  discretion,  and  which,  when  removed,  allows  the  mercury  to 


ALEXANDER'S  BAROMETER.  397 

flow  inward  or  outward  of  the  dish.     The  object  of  all  this  appa- 
ratus is  to  have  both  the  dish  and  the  tube  quite  full  of  mercury 
when  the  instrument  is  not  up  for  use ;  and 
the  elastic  bottom  is  intended  to  provide  for  Fig- 329- 

the  expansions  and  contractions  which  take 
place  upon  change  of  temperature,  to  which 
the  mass  is  always  more  or  less  subject.  The 
diameter  of  the  bottom,  therefore,  is  propor- 
tioned to  the  capacity  of  the  tube  and  dish  in 
such  sort  that  the  known  elasticity  of  the 
sheet  is  capable  of  adapting  it  in  close  contact  with  the  mercury 
within  through  a  range  of  60°  on  each  side  of  the  normal  tem- 
perature, which  may  be  taken  at  from  60°  to  62°  Fahr.  Such 
close  contact  may  be  expected  to  be  favorable  for  the  exclusion 
of  air. 

At  any  convenient  point,  say  within  a  half  inch  of  the  dish, 
the  zero  of  the  graduation  is  marked  on  the  tube,  upon  which 
also  the  division  of  the  graduation  is  marked  from  25  inches  up- 
wards to  31  inches  for  every  one-tenth.  A  loose  vernier  made 
of  pearl  (both  for  its  transparency  and  ease  of  motion),  and  made 
to  hug  the  tube  closely  by  a  circular  steel  spring,  subdivides  the 
graduation  to  7  Jn  of  an  inch,  which  is  supposed  to  be  minute,  all 
things  considered,  as  there  is  any  necessity  for.  The  closed  end 
of  the  tube,  which  is  shrunk  and  then  swelled  in  the  process  of 
sealing,  receives,  when  the  instrument  is  set  up,  and  is  embraced 
by  a  steel  collar  capable  of  being  drawn  tight  by  a  screw,  and 
having  a  sort  of  basket-handle,  as  in  the  Hassler  barometer,  a 
suitable  iron  bracket,  with  a  hook  and  nut  for  Fi  33Q 

elevating  or  depressing  the  tube  when  sus- 
pended, and  with  a  gimlet  screw  that  serves 
for  either  extempore  or  permanent  fastening 
of  the  bracket,  provides  the  means  of  support  both  for  the  tube 
and  for  the  thermometer,  as  in  the  former  case ;  and  finally,  an 
ivory  float,  shaped  like  a  hat  without  a  crown,  and  which  is  to  be 
slid  over  the  tube  before  the  collar  is  put  on,  and  whose  base 
must  correspond  to  the  zero  of  graduation,  completes  the  means 
of  adjustment,  Fig.  331.  In  order  to  effect  this  correspondence, 
another  mark  has  been  also  placed  upon  the  tube  a  certain  dis- 


398 


ALEXANDER  S   BAROMETER. 


Fig.  331, 


tance,  say  a  half  inch  above  zero,  exactly  equal  to  which  distance 
is  made  the  height  of  the  float  before-mentioned  from  its  base  to 
its  fiducial  edge.  Of  course,  when  said 
fiducial  edge  is  adjusted  to  the  mark  in 
question,  the  base  of  the  float  is  at  zero. 
And  as  this  base  is  in  contact  with  the  sur- 
face of  the  mercury  in  the  outer  cistern  or 
cup,  the  same  adjustment  determines  the 
mercury-surface  as  being  at  zero  likewise. 
When  the  instrument  is  to  be  set  up, 
and  is  just  taken  out  of  its  packing-case 
(which  is  a  wooden  sheath  suitably  lined), 
with  the  cistern  end  uppermost,  it  is  in- 
verted, and  held  at  an  angle  of  about  50° 
with  the  horizon,  its  cistern  is  plunged 
above  the  zero  mark  into  a  convenient  cup, 
or  basin,  or  outer  cistern,  containing  mer- 
cury. The  screw-plug  is  then  extracted 
under  the  mercury  by  means  of  an  appro- 
priate hook,  Fig.  332,  in  order  to  avoid 
soiling  the  metal  by  touching  with  the 
fingers ;  and  the  outward  flow  of  the  column 
and  its  descent  regulated  by  carefully 
raising  the  tube  to  the  vertical.  The  float 
is  then  slid  over  the  tube;  the  collar 
screwed  on ;  its  basket-handle  caught  by  the  hook  in  the  bracket 
previously  fastened  at  a  proper  height  above  the  cup ;  the  vernier 
applied ;  the  thermometer  immersed  in  the  mer- 

Fie  332 

cury  of  the  cup ;  and  after  five  minutes,  to  allow 
P  IQC3  of  its  assuming  the  temperature  of  the  fluid,  the 
column  is  ready  to  be  measured. 

When  the  instrument  is  to  be  taken  down,  the  same  steps  are 
gone  through  in  a  reversed  order ;  the  chief  caution  necessary 
being  to  see  that  the  tube  is  quite  full  to  the  very  top  (as  it 
always  becomes  at  the  suitable  inclination)  before  the  screw-plug 
is  inserted,  and  to  insert  said  plug  while  the  aperture  for  it  is 
beneath  the  surface  of  the  mercury. 

Such  are  the  principal  modifications  of  cistern  barometers 
requisite  to  be  mentioned.  Of  the  other  groups, — the  syphon- 


GAY-LUSSAC'S  BAROMETER.      -  399 

barometers, — a  sufficient  type  may  be  found  in  the  only  one  that 
will  be  described,  viz.,  Gay-Lussac's  Barometer. 

Cray  Lussac's  Barometer. — Of  this  form  of  instrument,  dis- 
embarrassed of  its  casing,  the  adjoining  sketch  -will  give  a  satis- 
factory illustration  ;  where  it  is  seen  to  be  composed  of  two  pieces 
of  an  ordinary  barometer-tube,  together  surpassing  33  or  34 
inches,  and  connected  by  a  re-curved  piece  of  glass  tube  with  a 
very  small  bore,  the  object  of  which  is,  by  increasing  the 
friction  as  well  as  diminishing  the  mass  of  the  column, 
to  dimmish  also  the  strain  or  shock  that  would  follow 
every  brusque  movement.  The  instrument  originally  is 
supplied  with  mercury,  rather  more  than  enough  to  fill 
the  upper  large  tube  and  the  capillary-tube,  including 
its  bend.  When  the  instrument  is  reversed  with  said 
bend  uppermost,  the  mercury  fills  the  bend  itself  en- 
tirely, thus  excluding  the  entrance  of  air,  and  the  sur- 
plus metal  drops  into  the  end  of  the  tube  near  o ;  at 
which  place  there  exists  a  small  orifice  for  the  admission 
of  the  atmosphere  to  press  on  the  column,  and  even  for 
additions  of  mercury  if  desirable,  but  too  small  and  in- 
troverted to  allow  the  escape  of  the  fluid  from  within  in 
any  of  the  reversals  which  the  instrument  may  undergo. 
The  sketch,  Fig.  333,  shows  the  apparatus  in  its  direct 
position,  when  the  column  in  the  upper  tube  will  have 
fallen  to  say  s,  and  will  stand  in  the  lower  one  at  say  t. 
It  is  evident  that  the  vertical  distance  between  the  surfaces  at  these 
two  points  is  the  height  of  the  column  of  mercury  which  equili- 
briates  the  pressure  of  the  atmosphere.  To  measure  this  there  are 
various  ways,  as  well  when  the  necessary  graduation  was  in- 
scribed as  at  first  upon  the  glass  as  when  it  is  marked  on  the 
other  brass  tube,  which  embraces  and  protects  it.  The  most 
usual  is  to  take  a  zero  midway  between  the  two  surfaces,  as  at  z, 
and  to  graduate  upwards  and  downwards  from  that  origin.  A 
movable  vernier  is  attached  to  each  scale,  which  is  adjustable  to 
the  surfaces  respectively,  and  subdivides  the  direct  readings :  the 
sum  of  the  two  readings  is  the  height  of  the  column  sought. 

The  instrument  is  enclosed,  together  with  a  thermometer  lying 
along  the  limb  s  z  (or  sometimes  the  thermometer  is  unattached), 
in  a  brass  tube,  which  is  slotted  for  some  distance  along  both 
limbs  to  allow  the  surfaces  to  be  seen  by  transmitted  light,  which 


400  MORLAND'S  DIAGONAL  BAROMETER. 

slots  are  coverable  with  a  portion  of  another  tube  moving  hori- 
zontally, and  serving  as  a  screen,  as  in  the  instance  of  the  wooden- 
cisterned  and  cased  barometers  spoken  of  just  now.  So  ar- 
ranged, it  is  ordinarily  capable  of  enduring  all  careful  transpor- 
tation and  even  ruder  treatment,  and  forms  one  of  the  neatest 
and  most  convenient  portable  barometers.  In  a  laboratory,  how- 
ever, where  this  feature  is  not  essential,  one  of  its  necessary 
defects  become  more  conspicuous,  viz.,  that  it  requires  two 
readings,  and  thus  doubles  the  time  and  trouble  of  observation. 

If  but  one  arm  were  read,  it  is  obvious  that  the  scale  would 
indicate  but  one-half  of  the  change  of  level  which  may  have  taken 
place  from  one  epoch  of  observation  to  another ;  for  of  the  total 
actual  movement  of  the  equilibriating  column,  equal  parts, 
whether  of  elevation  or  depression,  will  be  borne  in  just  recipro- 
cal senses  by  the  columns  in  the  two  limbs.  And  in  so  far  the 
errors  of  reading,  whatever  they  might  be,  would  be  multiplied. 
The  chances  of  such  multiplication  are  diminished  upon  the 
double  reading,  if  we  suppose  that  the  errors  are  liable  to  occur 
in  the  same  way,  as  is  most  likely.  If  such  supposition  is  not 
correct,  then  the  error  of  reading  will  be  of  course  multiplied. 

Such  errors,  which  are  always  possible,  partly  from  the  nature 
of  the  apparatus  and  partly  from  a  personal  proclivity  varying 
both  in  its  direction  and  its  amount  of  the  observer,  are  always 
to  be  guarded  against ;  and  this  aim  has  led  to  sundry  devices  for 
enlarging  the  scale,  and  thus  virtually  dividing  its  errors.  The 
wheel-barometer,  which  has  already  been  mentioned,  is  one  such 
device ;  where  a  range  of  one  inch,  for  instance,  in  the  vertical 
column  is  multiplied,  as  it  were,  in  the  revolution  of  the  index 
over  a  circumference  of  eighteen  inches.  A  similar  contrivance, 
applicable  to  the  syphon  barometer,'is,  instead  of  letting  the  float- 
string  be  connected  with  a  pulley  to  attach  it  to  the  short  arm  of 
a  balanced  lever,  whose  other  arm  may  bear  any  assignable  pro- 
portion in  length  to  said  short  arm,  and  the  circular  scale  tra- 
velled over  by  the  extremity  of  which  will  be,  of  course,  expanded 
in  the  same  proportion. 

Morlond^  Diagonal  Barometer. — Another  contrivance  for  the 
same  purpose  is  the  so-called  diagonal  barometer  of  Morland,  in 
which  the  upper  part  of  the  tube  instead  of  continuing  vertically 
is  inclined  to  the  horizon  at  any  angle,  and  the  scale  is  applied 


MORLAND'S  DIAGONAL  BAROMETER.  401 

to  the  inclined  limb.  It  is  clear  that  the  tube  must  be  made 
longer  than  the  ordinary  vertical  one,  in  the  ratio  of  the  angles 
of  inclination,  and  that  the  divisions  of  the  inclined  scale  will  be 
to  the  normal  ones  of  the  vertical  scale  in  the  proportion  of  the 
cotangent  of  those  angles  respectively  to  radius.  Another 
method  is  that  exhibited  in  the  rectangular  barometer,  as  it  is 
termed,  where  the  mechanical  arrangement  is  in  some  sense 
the  converse  of  the  last,  viz.,  the  open  end  of  the  tube  is  bent  for 
an  indefinite  extent  at  right  angles  to  the  vertical.  But  here  the 
multiplication  of  the  reading  is  in  the  ratio  of  the  square  of  the 
bore  of  the  vertical  and  horizontal  tubes  respectively ;  and  the- 
disparity  of  bore  is  either  produced  by  enlarging  considerably  the 
vertical  bore  through  the  range  of  its  possible  variation,  or  by 
diminishing  the  bore  of  the  horizontal  tube  until  it  becomes  even 
capillary.  If,  for  instance,  the  vertical  bore  be  040  inch,  while 
the  horizontal  is  0*05  inch,  it  follows  that  the  longitudinal  spaces 
to  contain  equal  quantities  of  mercury  must  be  64  times  as  great 
in  the  latter  as  in  the  former.  Of  course  the  scale  is  multiplied 
in  the  same  ratio.  In  this  arrangement,  the  smaller  the  calibre 
and  the  more  the  tube  is  kept  perfectly  horizontal,  the  less  occa- 
sion there  is  for  a  cistern ;  the  pressure  of  the  atmosphere  upon 
the  face  of  the  mercury  at  the  open  end  being  always  sufficient 
to  prevent  any  extravasation.  Such  extravasation  will  not  take 
place  even  with  the  swelled  vertical  bore,  under  ordinary  circum- 
stances. 

This  principle  of  varying  the  bore  of  the  tube,  so  as  to  produce 
motion  through  unequal  lineal  spaces,  coupled  with  another  of 
using  fluids  in  conjunction  with  mercury  of  vastly  inferior  specific 
gravity,  water,  tartrate  of  potassa  in  solution,  petroleum,  &c., 
has  been  very  fruitful  in  suggesting  modifications  for  expanding 
the  scale ;  and  the  names  of  eminent  geometers,  such  as  Des 
Cartes,  Huggens,  and  Hooke,  are  still  connected  with  arrange- 
ments to  this  end,  upon  which  they  exercised  no  inconsiderable 
ingenuity  in  invention  or  improvement.  But  the  description  of 
these  is  unnecessary  here;  for  at  the  period  of  their  suggestion 
the  application  of  the  barometer,  as  an  instrument  of  research, 
was  limited  and  partial,  and  its  destiny  but  vaguely  anticipated, 
so  that  a  cumbrousness,  which  would  now  be  found  intolerable, 
was  then  but  an  inconsiderable  defect,  while  the  very  amplifica- 

26 


402  ABIE'S  SYMPIESOMETER. 

tion  of  scale  by  the  means  resorted  to,  though  there  was  nothing 
left  to  be  desired  as  to  minuteness  of  reading,  introduced  errors 
of  another  a-nd  more  radical  kind,  of  which  there  was  at  that 
earlier  period  no  suspicion. 

Water  Barometer. — How  far  certain  modern  arrangements 
with  the  same  aim  are  to  be  classed  in  the  same  category  can 
only  be  judged  of  negatively,  in  consequence  of  their  limited  ac- 
ceptation. So,  for  instance,  the  great  water  barometer,  erected 
some  twenty  years  since  for  the  Royal  Society  of  London  by  Mr. 
Daniell,  remains  yet,  as  far  as  known,  unimitated.  The  extreme 
mobility  of  the  fluid  used  in  this,  and  the  magnitude  of  its  scale, 
— more  than  thirteen  times  that  of  a  mercury  column, — render 
its  oscillations  as  frequent  as  every  successive  breath  of  air  and 
as  capricious ;  while  the  evaporation  going  on  from  its  surface  no 
doubt  fills  with  an  atmosphere,  though  of  low  tension,  the  space 
that  ought  to  be  a  perfect  vacuum.  So,  too,  the  sulphuric  acid 
barometer  first  constructed  many  years  since,  and  recently  re- 
peated in  an  apparatus  at  the  Smithsonian  Institute. 

The  difficulties  which  have  attended  attempts  to  expand  the 
scale  of  the  barometer  in  using  mercury  or  lighter  fluids,  as  well 
as  some  other  practical  defects,  have  led  to  the  employment,  or 
more  correctly,  the  suggestion  of  substitute  apparatus,  in  which 
the  object  has  been  more  or  less  met  by  what  may  be  termed  in- 
direct methods.  Among  these  may  be  mentioned — 

Adies  Sympiesometer. — This  was  principally  intended  to  re- 
place the  ordinary  barometer  at  sea,  where  the  sudden  and  violent 
motions  of  the  vessel  render  the  oscillations  of  an  ordinary  mer- 
curial barometer  either  incapable  of  being  read  at  all,  or  not  very 
reliable.  These  motions,  therefore,  are  sought  to  be  counteracted 
in  such  a  column  by  strangulating  the  tube  in  some  convenient 
place  or  places,  or  zig-zagging  it,  or  twisting  it  in  a  spiral  after 
the  manner  of  Passement.  But,  although  the  movement  of  the 
column  may  be  thus  retarded,  so  as  to  insure  the  safety  of  the 
instrument  and  the  capacity  of  its  being  read,  this  gain  is  at  the 
expense  of  its  permanent  delicacy  and  susceptibility  to  minute 
atmospheric  variations  in  opposite  senses.  The  aim  of  the  sym- 
piesometer  is  to  cure  this  last  defect  also.  The  instrument  itself 
is  bulbed  at  both  ends  and  syphoned,  with  the  lower  bulb  open  to 
the  atmosphere.  The  upper  bulb  is  filled  with  pure  hydrogen ; 


ANEROID   BAROMETER.  403 

the  lower  one  in  part,  as  well  as  a  portion  of  the  upright  tube 
connecting  them,  with  almond  oil  colored  with  alkanet  root.  It 
is  obvious  that  as  the  pressure  of  the  atmosphere  upon  the  oil 
changes,  so,  inversely,  will  the  normal  volume  of  the  enclosed 
gas,  whose  limit  is  indicated  by  the  surface  of  the  oil  column, 
expand  or  contract ;  and  that  the  measure  of  compression  of  the 
gas  is  thus  indirectly  a  measure  of  the  pressure  of  the  atmosphere. 
Hence  the  name,  meaning  literally  "compression-measurers," 
which  has  been  given  to  it.  The  instrument  itself  is  graduated 
upon  comparison  with  a  mercurial  barometer  supposed  to  be  ac- 
curate ;  and  both  are  so  suitably  connected  with  an  air-pump  as 
to  make  an  artificial  stand  in  the  latter  of  successively  26,  27, 
28,  &c.,  inches,  and  the  cotemporaneous  stand  of  the  oil-column 
is  marked  on  the  sympiesometer-scale  as  corresponding  inches 
respectively.  These  spaces  are  then  subdivided  into  T-JC,  which, 
of  course,  correspond  to  O'Ol  inch  on  the  ordinary  mercurial 
scale.  Further,  the  volume  of  the  enclosed  gas  is  affected  not 
only  by  the  atmospheric  pressure,  but  also  by  changes  of  tempe- 
rature. To  save  the  necessity  of  calculating  a  correction  on  that 
account  an  ingenious  contrivance  has  been  arranged,  whereby  the 
inches-scale  of  the  column  slides  with  a  rack  worked  by  an  out- 
side knob  along  a  fixed  scale  marked  for  degrees,  counting  from 
above  downwards.  An  ordinary  thermometer  is  set  in  the  frame 
alongside  of  the  oil-tube,  and  in  observing  the  instrument,  a  zero 
or  index-mark  upon  the  sliding-scale  is  made  to  coincide  with  the 
identical  degree  on  the  fixed  scale  which  is  shown  upon  the  ther- 
mometer: the  reading  of  the  oil-column  upon  the  sliding-scale  is 
the  barometric  reading  required,  reduced  to  the  uniform  tempe- 
rature (32°  or  62°  F.),  which  may  have  been  adopted  for  the 
calculation  of  the  correction. 

There  is  no  doubt  of  the  sensibility  of  this  apparatus  to  very 
minute  changes  in  atmospheric  pressure ;  but  in  consequence  of 
the  liability  of  the  gas  to  absorption  by  the  oil,  it  is  not  so  cer- 
tain that  the  indications  remain  perfectly  uniform  during  a  long 
period,  or  that  they  are  permanently  accurate. 

Aneroid  Barometer.— This  sympiesometric  principle  has  been 
also  applied  to  another  class  of  devices,  known  as  aneroid  or 
fluidless  barometers.  The  first  suggestion  of  such  device  was 
about  a  century  ago  by  Mr.  Zeiher,  who  prepared  a  hollow  cylin- 


404  ANEROID    BAROMETER. 

der,  completely  freed  from  air,  with  two  movable  ends  kept  apart 
by  a  light  spring,  which  yields  as  the  atmospheric  pressure  in- 
creases, and  recovers  as  that  pressure  diminishes.     This  is  virtu- 
ally weighing  the  atmosphere  by  a  steel  yard,  whose  unavoidable 
friction  would  always  be  a  function  of  the  apparent  reading;  and 
it  seems  to  have  been  viewed  in  that  light,  and  to  have  remained, 
on  this  or  some  other  account,  a  mere  suggestion  for  another  half 
century,  when  Mr.  Conte'  took  it  up  afresh,  and  actually  caused 
it  to  be  executed, — a  form  which  he  denominated  a  vacuum  vase. 
This  was  a  lenticular  vase,  whose  sides  below  of  iron  or  copper, 
above  of  thin  sheet-steel,  were  kept  apart  by  a  series  of  springs. 
From  this  vase  the  air  was  exhausted,  and  the  vessel  soldered  up 
air-tight.     The  whole  weight  of  the  atmosphere  then  falls  'upon 
the  flexible  steel  arch ;  and  as  the  resistance  of  the  springs  was 
assumed  constant,  this  cover-plate  rises  or  falls  as  the  atmospheric 
weight  varies.     These  variations  are  shown  by  means  of  an  index 
which  vibrates  upon  a  suitable  dial-plate.     But  no  provision  was 
made  in  this  for  the  mechanical  effects  of  change  of  temperature 
in  altering  the  resistance  of  the  springs,  as  well  as  the  proportion 
of  the  parts  that  were  concerned  in  the  motion  of  the  index,  and 
the  irregularities  from  this  cause  forced  the  ingenious  inventor 
himself  to  acknowledge  the  insufficiency  of  the  apparatus. 

But,  nearly  a  half  century  afterwards,  another  Frenchman, 
M.  Vidi,  contrived  and  announced  an  instrument  to  which  he 
gave  specifically  the  epithet  aneroid,  which  was  just  now  used 
here  as  generic;  and  in  which,  by  making  the  sides  of  the  vacuum 
vase  not  arched  but  corrugated,  and  by  introducing  within  it  a 
permanent  gas  instead  of  metallic  springs,  and  by  connecting  its 
movement  with  springs  outside,  a  compensation,  in  some  degree, 
is  demonstrably  afforded  for  variations  of  temperature.  Thus, 
although  under  an  increased  temperature,  the  capacity  of  the 
vacuum  vase  tends  to  be  itself  increased,  and  so  by  expanding  to 
cause  the  index  to  move  in  a,  corresponding  direction,  the  dimi- 
nution of  elasticity,  both  in  the  sides  of  the  vase  and  in  the  spiral 
spring  seen  in  the  sketch,  allows  the  pressure  of  the  atmosphere 
to  be  more  effective,  so  that,  in  point  of  fact,  the  index  would 
move  in  the  opposite  direction,  were  it  not  checked  by  the  in- 
creased tension  of  the  contained  gas.  This  gas  tension,  then, 
between  the  two  opposing  results  of  increased  capacity  of  vase 


ANEROID   BAROMETER. 


405 


(and  thus  a  lifting  of  the  levers),  and  of  diminished  elasticity  of 
springs  (and  thus  their  depression),  is  left  to  hold  the  balance, 
and  in  its  proper  apportionment  to  cause  an  independent  result, 
which  is  strictly  symmetrical  with  the  variations  of  temperature 
to  which  it  is  subjected.  It  is  in  this  way,  at  least,  that  the 
principal  manufacturer  of  the  instruments,  Mr.  Dent,  accounts 

Fig.  334. 


for  the  regularity  with  which  an  aneroid  once  adjusted  follows  the 
corrected  readings  of  a  mercurial  barometer. 

Fig.  335. 


The  annexed  figures  334,  335,  and  336,  give  an  outside  sketch 


406 


BOURDON  S   BAROMETER. 


of  a  ground  projection  and  a  perspective  view  of  the  interior  of 
the  apparatus ;  in  which  D  shows  the  vacuum- vase,  c  the  lever, 
which,  resting  on  the  fulcrum  B  at  one  end,  and  on  the  spiral 
spring  S  at  the  other,  and  keyed  at  K  to  the  shaft  that  moves 
with  the  motion  of  the  vacuum-vase,  communicates  that  motion 


Fig.  336. 


through  the  vertical  rod  1,  the  arbor-levers  and  bow-piece  2,  3, 
4,  the  horizontal  rod  and  chain  to  the  arbor  of  the  index.  This 
arbor  is  kept  lively,  and  the  faculty  of  contrary  motion  in  the 
index  maintained  by  a  flat  spiral  spring,  which  is  seen  attached. 
The  readings  of  the  instrument  are  adjusted  to  those  of  a  mercu- 
rial barometer  by  means  of  a  screw,  which  is  at  the  centre  of  the 
back  of  the  case,  and  by  the  motion  of  which  the  index  also  can 
be  moved.  Of  the  two  hands  seen  on  the  dial,  the  steel  one  is 
the  cursive  index;  the  gilt  one  is  only  a  register-hand,  adjustable 
by  the  nut  on  the  outside  of  the  glass,  and  set  at  any  time  to 
correspond  with  the  cursive,  shows,  at  any  other  period,  the  vari- 
ation that  may  have  taken  place  in  the  pressure. 

Finally,  in  regard  to  the  reliability  of  this  apparatus,  it  must 
be  said  that,  in  spite  of  the  correctness  of  its  theory,  and  the 
very  ingenious  manner  in  which  the  mechanical  developments 
have  been  contrived,  it  is  hardly  to  be  accepted  as  under  all 
circumstances  an  invariable  substitute  for  the  mercurial  column. 

Bourdon's  Barometer. — The  metallic  barometer  of  Bourdon  is 


REGISTER  BAROMETERS.  407 

an  aneroid  arranged  upon  a  somewhat  different  mechanical  prin- 
ciple. Instead  of  the  vacuum-vase  being  a  flat  cylinder,  working 
by  its  face  as  in  Vidi's,  it  is  a  horse-shoe  hollow  lenticule,  the 
changes  of  atmospheric  pressure  upon  which  cause  the  ends  or 
heels  of  the  horse-shoe  to  approach  or  recede  from  one  another. 
These  approaches  and  recessions,  themselves  very  minute,  are 
multiplied  by  connecting-rods  that  work  a  winch-lever,  whose 
shaft  is  the  arbor  of  a  segment  of  a  toothed  wheel  working  into 
a  pinion  set  on  the  index  arbor. 

Wollaston  and  Regnault's  Barometer. — The  thermo-barometer 
of  Wollaston,  first  suggested  by  Fahrenheit  more  than  a  century 
and  a  quarter  ago,  and  recently  improved  by  Regnault,  and  from 
its  presumed  special  adaptation  to  the  measurement  of  heights, 
called  the  Hypsometric  (or  height-measuring)  Barometer,  acts 
in  a  still  more  indirect  manner,  and  furnishes  indications  that  are 
only  hypothetically  convertible  into  equivalents  of  a  mercurial 
column.  It  consists  of  a  thermometer  with  a  very  open  scale 
(degrees  divided  to  tenths  or  still  lower)  which  is  suitably  exposed 
to  the  vapor  of  boiling  water,  the  vessel  and  lamp  for  which  form 
part  of  the  apparatus.  The  thermometer  shows,  of  course,  the 
temperature  of  the  vapor  which  is  formed,  and  is  supposed  to 
show  its  temperature  at  the  crisis  of  boiling,  when  its  tension  is 
exactly  equal  to  the  atmospheric  pressure.  If  this  is  so,  and  if 
the  tension  of  vapor  at  varying  temperatures  were  accurately 
known,  or  even  uniformly  stated,  by  different  experimentalists  or 
theorists,  and  if  the  observation  were  momentaneous,  or  at  least 
but  brief,  the  instrument  would  be  a  commendable  and  valuable 
one.  Actually,  however,  it  is  not,  in  these  regards,  suitable  for 
use  in  the  laboratory,  and,  therefore,  need  not  be  farther  de- 
scribed here. 

For  the  laboratory,  an  apparatus  that  would  record  successive 
variations  in  atmospheric  pressure  would  be  exceedingly  useful ; 
and  devices  in  this  -aim  have  been  occasionally  tried,  under  the 
name  of — 

Register  Barometers.— But  the  friction  occurring  upon  the 
apparently  necessary  mechanical  arrangements  is  so  great  as 
seriously  to  impair  the  delicacy  of  the  instrument,  and  to  prevent 
the  reliable  use  of  any  of  the  contrivances  which  have  been,  up 


408  CONSTRUCTION   OF  BAROMETERS. 

to  this  time,  suggested,  and  whose  description  may  therefore  be 


After  this  account  of  different  forms  of  barometer,  which  all 
require,  more  or  less,  the  co-operation  of  a  professional  artist,  it 
will  be  well  to  explain  how  the  experimentalist  or  student  in  the 
laboratory  may  construct  for  himself  an  apparatus,  which,  with 
only  reasonable  skill  in  manipulation,  and  ordinary  good  fortune, 
will  be  capable  of  furnishing  results  as  reliable  and  convenient  as 
any  of  the  more  elaborate  arrangements  which  have  been  spoken 
of.  For  this,  a  tube  is  to  be  selected  (and,  if  possible,  from 
among  such  as  have  still  both  ends  sealed),  from  0*25  to  0-38 
inch  bore,  as  uniform  in  size,  and  as  free  from  strise,  and  as  thin 
in  the  material  as  may  be,  and  to  be  cut  off  (according  to  the 
methods  described  for  cutting  glass  tubes)  to  a  length  of  33  or 
34  inches.  The  open  end  is  then  to  be  ground  off  square  upon 
an  emery  plate.  About  an  inch  or  an  inch  and  a  half  from  the 
open  end,  a  suitable  mark  is  to  be  made  with  a  fine  file,  to  serve 
as  a  zero,  from  which,  with  a  beam  compass  or  an  accurate  fidu- 
cial-edged scale,  a  space  of  27  inches  is  to  be  laid  off  towards  the 
sealed  end  (care  being  taken  to  lay  the  line  as  nearly  in  the  axis 
of  the  bore  as  possible),  and  to  be  continued  inch  by  inch  up  to 
31  inches ;  which  inch  divisions  are  then  to  be  subdivided  from  a 
scale,  as  mentioned,  into  tenths.  For  making  these  divisions  ac- 
curately, it  is  best  to  coat  the  part  of  the  tube  where  they  are  to 
fall  with  a  thin  layer  of  beeswax,  or  a  strip  of  tissue  or  other 
thin  paper  may  be  laid  along  the  line,  and  cemented  to  the 
tube  with  lip-glue.  Upon  the  tube  so  prepared,  the  divisions  in 
question  are  first  transferred  with  a  pencil,  and  then  cut  into  the 
glass,  either  with  a  writing-diamond  or  a  dentist's  file.  Either  of 
these  implements  will  encounter  no  difficulty  in  any  tube  likely 
to  be  selected.  The  tube  so  graduated  is  then  to  be  carefully 
wiped  out  by  means  of  a  screw  ramrod,  wrapped  with  dry,  clean, 
old  linen,  and  all  specks  and  adhering  filaments  are  to  be  re- 
moved. 

Clean,  fresh  mercury  will  then  be  taken  and  sifted  into  the 
tube  against  the  side  of  the  glass,  so  as  to  cause  as  little  spatter- 
ing and  entanglement  of  air  as  may  be,  through  a  paper  funnel 
of  the  usual  shape,  and  of  a  reasonably  fine  orifice,  to  a  height  of 
5  or  6  inches  above  the  sealed  end ;  which  mercury  is  then  to  be 


CONSTRUCTION  OP  BAROMETERS.  409 

boiled  in  the  tube  itself  over  a  charcoal  fire,  or  better,  a  gas 
burner  of  sufficient  length  to  embrace  the  whole  reach  towards 
the  end  of  the  operation.  It  is  hardly  necessary  to  advise  that, 
in  order  to  promote  the  safety  of  the  tube,  it  should  have  been 
gradually  warmed  up  through  its  entire  length  before  urging  the 
mercury  to  ebullition.  When  all  bubbles  of  air  cease  to  be  given 
off,  more  mercury,  previously  heated,  is  to  be  similarly  sifted  in 
to  a  height  of  15  or  18  inches,  and  treated  like  the  preceding 
instalment ;  after  which  a  last  addition  is  to  be  made,  filling  the 
tube  to  (say)  3  inches  of  the  top,  or  open  end,  and  boiled  as 
before.  Care  is  to  be  taken  that  each  successive  boiling  should 
be  initiated  below  the  joint,  as  it  were,  of  the  successive  additions 
to  the  column,  in  order  to  avoid  driving  any  of  the  entangled  air 
downwards.  The  ebullition  cannot  be  effected  in  the  last  three 
inches  of  the  tube ;  and  all  that  can  be  done  is  to  sift  into  that 
until  running  over  hot  mercury,  which  has  been  recently  boiled 
in  a  separate  vessel,  and  to  apply  below  and  about  the  joint  as 
much  heat  as  can  be  borne  without  extravasation  of  the  fluid. 
Placing,  then,  against  the  end  of  the  tube,  in  such  a  manner  as 
not  to  cause  any  violent  removals  or  out-splashings  of  the  mer- 
cury, the  end  of  the  middle  finger,  covered  with  a  clean  buckskin 
or  kid  glove,  or,  still  better,  such  a  padded  implement  as  is 
figured  under  the  preceding  description  of  the  Alexander  barome- 
ter, the  tube  is  to  be  inverted  and  its  end  plunged  in  a  porcelain 
or  glass  cistern,  cup,  or  basin,  which  has  been  previously  supplied 
with  a  suitable  quantity  of  boiled  mercury,  whose  specific  gravity 
has  been  ascertained  and  recorded ;  and  when  raised  vertical, 
the  finger  or  pad  to  be  carefully  withdrawn,  so  as  to  let  down  the 
column  easily  and  without  shock.  Then,  the  tube  being  held  by 
an  assistant,  sufficient  wire  or  silk  cord  is  to  be  wrapped,  whip- 
maker  fashion,  round  the  sealed  end  of  the  tube,  to  form  a  loop 
for  suspension,  which  loop  can  be  hung  upon  a  hook  in  a  conve- 
nient bracket,  made  as  described  for  the  barometer  just  men- 
tioned, or  in  the  absence  of  such  a  contrivance  on  a  permanent 
hook,  in  which  case  the  adjustment  will  be  made  either  in  moving 
the  cistern  itself  by  wedges  under  it,  or  by  adding  or  withdrawing 
portions  of  the  mercury  within.  As  the  barometer  is  intended  to 
be  stationary,  this  adjustment  once  made  does  not  require  to  be 
often  repeated,  though  it  should  be  verified  for  every  series  of  ob- 


410 


BAROMETERS. 


Fig.  337. 


Fig.  338. 


servations.  The  easiest  way  of  making  such  adjustment  is  by 
the  ivory  float  already  described,  the  fiducial-edge  in  the  notch 
of  which  is  to  be  made  to  correspond  with  a  mark  made  on  the 
tube  of  the  same  distance  from  zero  as  the  space  between  said 
edge  and  the  base  of  the  float ;  the  most  accurate  way  is  by 
means  of  a  vertical  ivory  stiletto,  gauged  to  a  certain  height  on 
the  tube,  and  attached  by  a  horizontal  arm  to  a  metal  or  ivory 
collar  clamped  on  the  tube  after  the  method  of  Fortin. 

After  this  adjustment,  made  in  either  way,  the  column  can  be 
read  directly  to  inches  and  tenths,  and  lower  by  estimation.  To 
subdivide  accurately  and  directly  resort  must  be  had  to  a  vernier, 
which  may  be  a  thin  slip  of  pearl  or  ivory,  or  even  paper,  on 
which  a  space  of  0*9  inches,  or  nine  divisions  of  the  scale  is,  by 
proportional  compasses  or  by  any  other  satisfactory  method, 
divided  into  ten  equal  parts.  It  is  manifest  that  each  one  of 
these  parts  is  j^  of  an  inch  shorter  than  the  scale  division ; 
that  if  the  zero  of  the  vernier  corre- 
sponds with  any  scale-division,  such 
correspondence  cannot  occur  again 
until  its  tenth  division ;  and  that 
when  the  zero  does  not  so  correspond, 
the  number  of  the  vernier  division, 
which  coincides  with  some  scale  di- 
vision, indicates  the  number  of  hun- 
dredths  by  which  the  zero  happens 
to  deviate  and  exceed  the  nearest 
scale  division  below  it.  This  will  be 
made  plainer  by  reference  to  the 
adjoining  cuts,  in  which  vernier  and 
scale  are  represented  in  the  two  po- 
sitions respectively.  In  (1)  the  zero 
of  the  vernier  divisions  is  seen  to  co- 
incide with  29-5  on  the  scale  ;  vern. 
div.  1  is  of  course  0*01  in.  short  of  29*6 ;  vern.  div.  2  short  by 
0-02  in.  of  29-7;  vern.  div.  3  short  by  0-03  in.  of  29-8;  and  so 
on  until  vern.  div.  9  is  short  by  0-09  in.  of  30'3,  and  vern.  div. 
10  coincides  with  304.  Now  if,  as  must  be  universally  attended  to, 
the  zero  of  the  vernier  is  adjusted  to  the  level  of  the  mercury  in 
the  tube,  position  (1)  gives  a  reading  for  the  height  of  the  column 


BAROMETERS.  411 

of  29-50  inches.  In  position  (2)  the  vernier  zero  presupposed 
to  have  been,  in  like  manner,  independently  adjusted  to  the  mer- 
cury-level in  the  tube,  does  not  happen  to  coincide  with  any  scale 
division,  but  lies  rather  more  than  midway  between  29-5  and  29-6. 
In  order  to  see  by  how  many  hundredths  exactly  this  zero  or 
mercury-level  deviates  from  and  transcends  29*5,  the  observer 
looks  along  the  scale  until  he  finds  a  division  there  coincident 
with  some  vernier  division  ;  the  number  of  said  vernier  division 
is  the  number  of  hundredths  in  question.  It  is  seen  here  that 
division  6  of  the  vernier  coincides  with  a  division  (it  is  immaterial 
to  count  which)  on  the  scale,  and  T50  is  therefore  the  space  by 
which  vern.  0  has  passed  29-5,  and  the  proper  reading  is  29-56 
inches.  If  the  student  is  not  familiar  with  vernier  reading,  and 
finds  a  difficulty  or  want  of  readiness  yet  remaining  after  this 
attempted  explanation,  the  best  method  for  him  is  to  draw  the 
two  scales  on  separate  pieces  of  paper,  so  as  that  one  (the  vernier) 
may  be  applied  to  and  shifted  along  the  other.  He  cannot  fail 
after  a  few  trials  to  catch  the  idea  and  the  knack  of  this  indis- 
pensable adjunct,  the  vernier,  in  measuring  spaces  that  are  too 
minute  for  direct  graduation. 

In  the  arrangement  here  given,  the  reading  does  not  answer 
for  less  than  hundredths  of  an  inch.  Fortunately,  a  greater 
minuteness  is  not  requisite  in  any  ordinary  physical  research ;  and 
if  it  were,  there  is  room  to  question  its  attainability  otherwise 
than  as  a  formal  precision  not  a  substantial  accuracy. 

A  barometer,  made  and  mounted  as  recommended,  will  give 
better  than  most  of  the  more  elaborate  instruments  all  the  indi- 
cations which  are  presumed  to  denote  that  the  essential  condi- 
tions of  a  perfect  apparatus  have  been  satisfied.  These  indications 
are  principally  the  brilliance  of  the  mercurial  column,  for  the 
observation  of  which  the  naked  tube  affords  the  utmost  scope 
possible  ;  a  peculiar  hammer  or  click  made  by  the  impact  of  the 
mercury  column  against  the  sealed  end  when  the  instrument,  pre- 
viously stoppered  by  the  pad  or  the  gloved  finger,  is  lifted  out  of 
the  cistern  and  gently  inverted,  which  click  cannot  be  produced 
if  there  is  any  appreciable  residual  air  in  the  space  intended  to 
be  vacuous ;  the  adherence  of  the  mercury  column  to  the  sealed 
end  when  the  tube  reverts  to  its  erect  position,  and  which  some- 
times requires  a  considerable  concussion  to  be  overcome ;  the  phe- 


412  BAROMETERS. 

nomenon,  in  the  dusk  or  dark,  of  luminous  green  flashes  when, 
the  tube  being  normally  suspended  and  caused  to  swing  through 
a  small  arc,  the  mercury  column  vibrates  within,  and  electrically 
excites  the  tube ;  and  finally,  the  manifestation  in  broad  day- 
light of  electric  attraction  and  repulsion,  when  to  the  tube  so 
swinging  a  gold-leaf  electrometer  is  presented.  By  the  preva- 
lence of  all  these  signs,  the  vacuum  is  judged  to  be  more  or  less 
perfect ;  and  when  this  condition  of  perfection  is  attained,  all  the 
other  details  of  arrangement  are  only  matters  of  fancy,  conveni- 
ence, or  conservatism. 

This  last  item,  to  be  sure,  viz.,  the  conservation  of  a  vacuum 
once  attained  is  hardly  less  interesting  than  the  original  attain- 
ment; and,  unfortunately,  the  deterioration  of  tolerably  good 
barometers  is  more  frequent,  constant,  and  uniform,  than  the 
occurrence  of  instruments  of  a  higher  class.  This  deterioration, 
by  whatever  symptoms  manifested,  seems  to  be  attributable  alto- 
gether to  the  action  of  the  atmosphere,  as  well  chemical  as 
mechanical.  The  first  produces  an  oxidation  of  the  metal  in  the 
cistern  (supposing  the  column  entirely  exempt  from  contact  with 
air)  which  does  not  fail,  after  a  longer  or  shorter  period,  under 
ordinary  circumstances,  to  be  propagated  upwards  in  the  tube ; 
the  second  (under  the  same  supposition)  is  always  active  in  in- 
sinuating minute  portions  of  air,  favored  by  every  oscillation 
of  the  column  and  the  motion  of  the  tube,  downward  along  the 
outside,  and  upward  along  the  inside  of  the  tube.  If  the  assump- 
tion of  a  perfect  vacuum  within  does  not  hold  in  fact,  of  course 
the  operation,  in  the  first  mentioned  mode,  and  possibly  also  in  the 
second,  is  proportionally  facilitated.  It  was  at  one  time  supposed, 
upon  authority  no  less  high  than  Davy  himself,  that  atmospheric 
air  was  always  combined,  as  it  were,  vesicularly  in  every  mass  of 
mercury,  and  that  all  attempts  to  expel  it  by  heat  or  withdraw 
it  by  exhaustion  would  be  ineffectual;  but  the  later  experimental 
researches  of  Daniell  have  shown  that  this  supposition  was  an 
error,  and  that  the  attraction  between  the  mercury  and  the  acci- 
dentally contained  air  is  not  difficult  to  be,  by  proper  means, 
entirely  overcome.  The  air,  then,  which  deteriorates  the  vacuum 
and  spoils  the  column,  creeps  in  from  without ;  and  when  it  is 
considered  that  there  is  no  liquid  contact  between  the  metal  and 
the  glass, — no  wetting  of  the  latter  by  the  former, — one  can 


BAROMETERS.  413 

readily  see  that  in  the  finite  space  which  always  thus  occurs  be- 
tween the  two  surfaces  at  every  point  of  the  immersed  part  of  the 
tube  there  is  ample  room  for  air  to  insinuate  itself  between  them, 
and  thus  to  leak  into  the  tube.  With  respect  to  oxidations  within 
the  tube,  which  manifest  themselves  by  a  loss  of  brilliance  of  the 
column  though  its  smoothness,  is  still  maintained,  they  may,  in 
some  cases,  arise  from  a  partial  amalgamation  with  the  lead  used 
in  the  composition  of  the  glass.  When  there  is  opportunity  for 
this,  the  disorder  is  hopeless,  and  after  it  has  reached  a  certain 
point  the  barometer  is  no  longer  reliable,  and  the  tube  should  be 
rejected.  But,  with  respect  to  leaks  occurring  round  the  open 
end  of  the  tube,  the  platinum  guard  spoken  of  under  the  Alexan- 
der barometer,  and  whose  suggestions  arose  with  Mr.  Daniell, 
appears  to  present  a  full  remedy.  The  amalgamation  which 
takes  place  with  platinum  is  very  slight  and  slow,  the  amal- 
gam itself  of  great  specific  weight ;  an  air-tight  liquid  contact  is 
therefore  effected  along  the  whole  width  of  the  platinum  strip, 
and  whatever  amalgam  may  at  any  time  be  detached,  tends  to  the 
bottom  of  the  cistern  instead  of  ascending  like  the  lead  amalgam 
to  the  surface. 

The  opinion  just  now  referred  to,  of  an  indestructible  combina- 
tion between  mercury  and  certain  finite  portions  of  air,  had  its 
influence  at  the  time  upon  the  question  of  boiling  the  mercury  in 
the  tube,  as  a  means  of  obtaining  a  more  complete  and  perma- 
nent vacuum  ;  and  those  who  objected  to  the  boiling,  on  the  score 
of  its  undoubted  trouble  and  risk,  were  all  the  more  fortified  in 
their  objections  by  the  conviction  of  its  inutility.  But  the  re- 
searches of  Mr.  Daniell  have  almost  dispelled  such  convictions ; 
while  they  have  also  brought  to  light  an  important  advantage  to 
be  derived  from  boiling,  viz.,  in  diminishing  the  correction  that 
has  to  be  applied  for  what  is  technically  called  Capillarity.  This 
term,  although  not  literally,  is  yet  physically  applicable  as  well  to 
barometer  tubes  of  the  largest  ordinary  bore  as  to  those  minutely 
pierced  stems,  whose  hair-like  orifices  are  properly  and  strictly 
to  be  named  capillary,  and  the  correction  is  necessary  in  both  to 
compensate  for  the  effect  arising  from  the  relative  attractions 
reciprocal  between  the  tube  and  the  enclosed  fluid,  and  existing 
among  the  molecules  of  the  fluid  themselves.  If  the  physical 
sum  of  these  attractions  respectively  be  equal  (or,  to  speak  geo- 


414  .        BAROMETRIC  CORRECTIONS. 

metrically  and  with  more  precision,  if  the  intensity  of  the  attrac- 
tive force  of  the  matter  of  the  tube  is  half  of  that  of  the  fluid)  the 
surface  of  the  column  will  of  course  be  plane  and  horizontal, 
there  being  no  force  to  solicit  it  towards  any  other  form.  If  the 
attraction  of  the  tube  be  null  or  very  small  compared  with  that 
of  the  fluid,  the  surface  will  be  convex  and  nearly  hemispherical, 
its  radius  of  curvature  increasing  with  the  tube-attractiveness, 
while  that  of  the  fluid  remains  constant,  until  the  former  element 
becomes  equal  to  half  the  latter.  From  this  epoch,  which  is  that 
of  horizontally,  if  the  tube-attractiveness  goes  on  increasing, 
the  surface  becomes  proportionately  concave,  and  attains  hemi- 
sphericity  when  the  intensities  of  the  respective  forces  are  nume- 
rically equal.  Hence,  with  mercury,  upon  which  glass  exercises 
little  or  no  force  of  attraction,  the  surface  of  the  column  is  convex, 
and  is  depressed,  or,  as  it  were,  repelled  below  its  proper  and 
otherwise  normal  level.  With  water,  on  the  other  hand,  oils  and 
all  liquids  which  wet  glass,  the  surface  is  concave,  and  is  elevated 
above  said  normal  level. 

As  the  attractions  in  question  are  not  sensible  through  spaces 
which  are  considerable,  and,  in  point  of  fact,  are  inappreciable  at 
appreciable  distances,  their  effect  will  be  proportionate  to  the 
diameter  of  the  tube,  and  when  that  diameter  surpasses  (say) 
0*75  inch  it  becomes  insensible,  and  the  correction  unnecessary. 
But,  in  any  case,  if  the  diameter  be  assumed  uniform  (for  other- 
wise there  would  be  successions  of  varying  equilibrium,  stable  and 
unstable,  in  the  tube)  as  well  as  the  quantities  of  the  respective 
intensities,  the  amount  of  the  correction  is  theoretically  capable 
of  calculation,  and,  if  suitable  experimental  data  be  substituted, 
of  numerical  definition.  Such  definition  is  to  be  found  in  the 
following  table,  founded  on  the  formula  of  Laplace,  and  the  ob- 
servations of  Gay-Lussac  and  Haiiy,  calculated  by  Bouvard,  and 
here  for  the  first  time  reduced  and  interpolated  for  English  mea- 
sures. 

CORRECTIONS  FOR  CAPILLARY  DEPRESSION  IN  BAROMETER  TUBES. 


TUBE. 
Bore.     •  Unboiled.  Boiled. 

In.  In.  In. 

0-16         .         .         0-080  0-040 

0-18         .         .         0-068  0-034 

0-20  0-058  0-029 


TUBE. 

Bore.                            Unboiled.  Boiled. 

In.                                    In.  In. 

022         .         .         0-050  0-025 

0-24         .         .         0-044  0-0-22 

0-2G                           0-038  0-019 


BAROMETRIC  CORRECTIONS. 


415 


Bore. 
In. 

0-28 

0-30 
0-32 
0-34 
0-36 
0-38 
0-40 
0-42 
0-44 


TUBE. 

Unboiled. 
In. 
0-034 

Boiled. 
In. 
0-017 

Bore. 
In. 

0-46 

0-030 

0-015 

0-48 

0-026 

0-013 

0-50 

0-023 

00115 

0-52 

0-020 

o-oio 

054 

0-018 

0-009 

0-56 

0-016 

0-008 

0-58 

0-014 

0-007 

0-60 

0-012 

0-006 

In. 

0-011 


TUBE. 
Unboiled.          Boiled. 

In. 

•00055 
0-010  0-005 

0-009 
0-008 
0-007 
0-006 
00055 
0-005 


0-0045 

0-004 

0-004 

0003 

0003 

0-003 


The  3d  and  6th  columns  of  this  table  are  in  accordance  with 
Mr.  Daniell's  observations,  which  authorize  us  to  conclude  that 
the  effect  of  boiling  in  the  tube  is  to  augment  the  attraction  of 
the  tube  for  the  mercury  (probably  by  causing  a  more  intimate 
contact),  and  thus  to  diminish  the  correction,  as  nearly  as  may 
be,  to  one-half  of  what  would  be  required  in  unboiled  tubes. 
These  last  columns,  then,  are  what  should  be  used  in  the  labo- 
ratory. 

It  is  hardly  necessary  to  say,  that  with  a  syphon-barometer  a 
correction  of  this  kind  is  not  applicable,  provided  the  bore  of  the 
two  arms  be  the  same.  And  it  is  as  little  proper  here  to  discuss 
a  suggestion  which  readily  follows  what  has  been  said,  viz.,  that 
with  a  cistern-barometer  of  the  kind  recommended  just  now,  it 
would  not  be  difficult,  under  given  conditions  of  bore  and  cistern- 
diameter,  to  give  such  a  weight  to  the  float  as  to  correct  mecha- 
nically the  capillary  depression,  or,  what  is  still  easier,  provided 
the  fact  be  noted  on  the  instrument  to  make  the  corresponding 
correction,  either  in  the  zero  of  the  graduation  or  in  the  height 
between  the  bore  and  the  fiducial-edge  of  the  float. 

There  is  another  correction  which  cannot,  in  the  same  or  any 
other  way,  be  dispensed  with  or  obviated,  and  which  is  necessary 
to  compensate  the  increased  height  and  expansion  of  the  mercu- 
rial column  by  heat,  in  order,  first,  for  any  individual  observation 
to  reduce  the  apparent  reading  to  what  it  would  have  been  had 
there  been  no  change  in  the  volume  of  the  mercury,  and  thus 
show  the  height  of  column  which  at  the  normal  specific  gravity 
equilibriated  the  atmosphere ;  and  secondly,  to  yield  observations 
which,  whether  at  the  same  place,  but  at  different  temperatures, 
or  at  different  places  either  at  the  same  or  at  different  tempera- 


416- 


BAROMETRIC   CORRECTIONS. 


tures,  are  thus  made  fairly  comparable.     This  is  best  done  by  a 
table  like  the  following : 

BAROMETRIC    CORRECTIONS    FOR  TEMPERATURE. 


Therm. 
Fahr. 

BAROMETRIC  COLUMN. 

28  in. 

28-5 

29  in. 

29-5 

30  in. 

30-5 

31  in. 

31-5 

In. 

In. 

In. 

In. 

In. 

In. 

In. 

In. 

0° 

0-077 

0-078 

0-080 

0-081 

0-082 

0084 

0-085 

0-086 

5 

0-065 

•066 

•067 

•068 

•069 

•071 

•072 

•073 

10 

•053 

•054 

•055 

•056 

•057 

•058 

•058 

•059 

15 

•041 

•042 

•042 

•043 

•044 

•044 

•045 

•046 

20 

•029 

•029 

•030 

•030 

•031 

•031 

•032 

•032 

25 

•017 

•017 

•017 

•018 

•018 

•018 

•019 

•019 

30 

+  0-005 

0005 

0-005 

0-005 

0-005 

0005 

0-005 

0-005 

35° 

—  0-007 

0-007 

0-007 

0-008 

0-008 

0-008 

0-008 

0-008 

40 

•019 

•020 

•020 

•020 

•021 

•021 

•021 

•022 

45 

•031 

•032 

•032 

•033 

•033 

•034 

•035 

•035 

50 

•043 

•044 

•045 

•046 

•046 

•047 

•048 

•049 

55 

•055 

•056 

•057 

•058 

•059 

•060 

•061 

•062 

60 

•067 

•068 

*)70 

•071 

•072 

•073 

•074 

•076 

65 

•079 

•081 

•082 

•083 

•085 

•086 

•088 

•089 

70 

•091 

•093 

•094 

•096 

•098 

•099 

•101 

•103 

75 

•103 

•105 

•107 

•109 

•111 

•112 

•114 

•116 

80 

•115 

•117 

•119 

•121 

•123 

•126 

•128 

•130 

85. 

•127 

•130 

•132 

•134 

•136 

•139 

•141 

•143 

90 

•139 

•142 

•144 

•147 

•149 

•152 

•154 

•157 

In  constructing  this  table,  the  melting-point  of  ice,  or  32° 
Fahr.,  has  been  taken  as  a  standard  of  temperature  to  which  the 
observations  are  to  be  reduced.  For  all  temperatures  below  32° 
the  corrections  shown  in  the  table  are  additive  to  the  actual  read- 
ing ;  for  all  above  32°  they  are  sultr active.  The  temperatures 
are  given  only  from  5°  to  5° ;  for  any  required,  it  will  be  suffi- 
cient to  take  proportional  parts  of  the  differences  between  the 
two  corresponding  nearest  corrections,  above  and  below;  for 
which  purpose  it  is  that  the  quantities  are  expressed  in  thou- 
sandths. Similar  proportional  parts  maybe  taken  as  between  the 
columns  nearest  above  and  below  to  the  actual  barometric  reading; 
but  this  is  by  no  means  necessary  in  ordinary  cases.  The  quantities 
in  any  column  rule  for  any  barometric  stand,  at  or  above  the  cap- 
tion there,  until  it  attains  the  next  half  inch  in  the  adjoining  one. 
Thus,  suppose  it  be  required  to  correct  a  reading  of  the  baro- 
meter of  29-75  made  at  68°  F.  Look  in  the  col.  of  29-5,  the 
nearest  one  below,  where  the  corr.  for  65°  is  seen  as  0'083  in., 
while  that  for  70°  is  0-096  in.,  and  the  difference  between  the 


SOLUTION.  417 

two  quantities  is  0-013  in.,  corresponding  to  5°.  The  propor- 
tional parts,  then,  for  3°  (the  diff.  between  65°  and  68°)  will  be 
(I.  0-013  =)  0-004 ;  and  (0-083  +  0-004  =)  0-087  is  thus  found 
for  the  tube  correction,  and  (29-75  —  0-09  =)  29-66  the  corrected 
reading  reduced  to  32°  F.  If  it  be  desired  to  have  the  reduction 
for  some  other  standard  than  32°,  the  table  will  still  serve  for 
any  case  where  very  minute  precision  is  not  required,  if  used,  as 
it  were,  by  double  entry,  that  is,  reducing  at  first  to  32°  by  sub- 
tracting, if  the  temperature  is  above,  and  vice  versa;  and  then 
raising  that  reduced  temperature  to  the  standard  in  question  by 
reversing  the  process.  So,  if  it  be  required  to  reduce  the  read- 
ing given  just  now  to  say  62°  F.,  the  process  has  already  given 
29-663  as  at  32°  ;  the  correction  tabulated  for  60°  is  0-071,  and 
the  proportional  part  for  2°  is  (f .  0-012  =)  0-005,  making  the 
whole  correction  0-076,  which,  added  to  29-663,  gives  29-74  as 
the  corrected  reading  for  a  temperature  of  62°. 


CHAPTER  XX. 

SOLUTION. 

WHEN  a  substance  added  to  a  liquid  is  wholly  or  partially 
taken  up  by  that  liquid,  it  is  said  to  be  soluble  therein.  The 
liquid  employed  is  termed  the  solvent,  and  its  combination  with 
the  dissolved  particles,  a  solution  ;  and  if  the  liquid  has  exerted 
its  solvent  power  to  the  fullest  extent,  then  the  solution  which  it 
forms  is  said  to  be  saturated,  because  it  can  hold  no  more. 

The  variable  degree  of  solubility  in  different  liquids  serves  a» 
a  distinctive  characteristic  of  bodies,  particularly  those  which  are 
solid. 

Solution  is  either  wholly  mechanical,  or  else  chemico-mecha- 
nical.1  In  the  first  case,  it  is  a  molecular  division  of  a  body,  or, 
in  other  words,  a  diffusion  of  its  particles  in  an  appropriate  liquid 
without  any  alteration  of  its  original  properties,  save  as  to  form 

1  Many  chemists  contend  that  "  all  solution  is  chemical  union  f  and  on  this  point 
the  reader  is  referred  to  a  paper,  by  T.  S.  Hunt,  in  Silliman's  Journal  lor  January, 

1855. 

27 


418  SOLUTION. 

and  cohesion.  Thus,  for  example,  an  aqueous  solution  of  sugar 
or  salt  yields  the  whole  of  its  charge  by  EVAPORATION,  and  one 
of  sulphate  of  lime  by  the  addition  of  alcohol,  in  which  it  is  in- 
soluble. Ethereal  or  spirituous  solutions  deposit  their  dissolved 
matter  by  DISTILLATION  or  CRYSTALLIZATION;  and  some  other 
kinds,  that  of  gutta-percha  in  chloroform,  for  instance,  by  PRE- 
CIPITATION with  ether  or  alcohol.  When  the  dissolved  particles 
are  thus  recoverable  again  in  an  unaltered  state,  chemically  con- 
sidered, their  solution  may  be  styled  simple. 

In  the  second  case,  chemico-mechanical  solution,  in  contradis- 
tinction to  that  which  is  purely  mechanical,  is  a  process  requiring 
the  modification  of  a  body  by  chemical  action  previous  to  its 
solution.  Thus,  for  example,  copper,  iron,  or  any  other  base  or 
acid,  insoluble  in  the  ordinary  solvents,  may  be  readily  taken  up 
by  liquid  acids  or  bases.  But  the  liquid  holds  in  solution  a  newly 
formed  body  entirely  dissimilar  to  the  original  substance  in  pro- 
perties, as  appears  when  it  is  separated.  In  this,  therefore,  con- 
sists the  difference  between  a  simple  or  mechanical  and  a  chemico- 
mechanical  solution.  As  examples  of  this  latter,  iron  may  be 
dissolved  in  dilute  sulphuric  acid,  but  in  the  act  is  transformed 
into  copperas ;  alkalies  are  taken  up  by  acids,  but  become 
altered  to  salts  ;  and  oil  in  being  dissolved  by  potassa  solution  is 
changed  into  soap.  Hence  it  is  that  the  chemical  reaction  is  a 
preliminary  step  requisite  to  promote  simple  solution.  The  point 
of  saturation  in  chemical  solution  is  that  at  which  the  two  bodies, 
invariably  of  opposite  properties,  have  combined  in  proportions 
adequate  to  neutralization. 

There  are  some  exceptions  to  the  above,  which  refer  to  certain 
instances  in  which  the  acids  and  alkalies  act  as  mere  simple  sol- 
vents, and  without  changing  the  original  properties  of  the  dis- 
solved substance.  For  example,  acetic  acid  dissolves  certain 
phosphates  and  borates;  aqua  ammonite  takes  up  carmine; 
potassa  water  the  hydrated  peroxide  of  tin ;  and  hydro-sulphuret 
of  ammonia  the  deutosulphuret  of  iridium. 

Solution  is  one  of  the  most  important  processes  in  chemistry ; 
it  not  only  facilitates  chemical  reaction,  but  allows  the  separation 
of  soluble  from  insoluble  bodies,  or  parts  of  the  same ;  and  conse- 
quently the  purification  of  the  solution  by  subsequent  FILTRATION, 

EVAPORATION,  and  CRYSTALLIZATION. 


SOLUTION.  419 

As  regards  the  power  of  dissolving  the  greatest  number  of 
substances,  water  is  the  first  in  the  rank  of  simple  solvents, 
alcohol  the  next,  and  ether  third.  Then  follow  spirits  of  turpen- 
tine, pyroxylic  spirit,  the  volatile  and  fixed  oils,  chloroform,  ben- 
zole, and  a  host  of  other  liquids  suitable  to  particular  substances. 
Of  the  alkalies,  aqua  ammonias  or  potassa  are  most  used;  the 
former  preferably,  because  of  its  volatility  and  that  of  most  of 
its  salts.  All  of  the  common  acids  are  employed,  though  some 
few  only  are  of  general  application :  such  as  the  muriatic,  nitric, 
sulphuric,  acetic,  and  tartaric. 

When  the  solubility  of  bodies  is  spoken  of,  it  is  in  reference 
usually  to  water,  that  being  the  standard  liquid.  In  testing  the 
solubility  of  a  substance,  it  is,  therefore,  usual  to  commence  with 
that  liquid,  and  if  it  fails,  to  proceed  with  the  next  in  order ; 
and  always,  for  reasons  below  given,  trying  the  experiment  at 
varied  temperatures,  with  gradually  increased  quantities  if  ne- 
cessary. 

A  very  convenient  way  of  testing  the  solubility  of  a  substance 
is  by  means  of  a  test-tube.  If  solid,  a  small  portion  in  powder 
is  to  be  introduced  and  covered  with  distilled  water,  or  the  sol- 
vent to  be  used,  and  repeatedly  agitated  by 
the  hand,  the  forefinger  closing  the  mouth 
(Fig.  339)  to  prevent  the  escape  of  particles. 
If  the  matter  is  wholly  soluble,  there  will  be 
no  deposit  at  the  bottom  of  the  tube ;  if  par- 
tially soluble,  the  substance  will  have  decreased 
in  bulk ;  if  totally  insoluble,  it  will  occupy 
the  same  space  as  at  first.  To  determine  as 
to  the  two  latter  results,  a  minute  portion  of 
the  supernatant  liquid  is  decanted  and  evapo- 
rated in  a  small  platinum  spoon  or  strip  of  window-glass  over  the 
spirit-lamp  (Fig.  151) ;  if  a  residue  remains  it  indicates  that  mat- 
ter has  been  taken  up. 

When  heat  is  required,  the  lamp  (as  at  Fig.  153)  affords  a 
convenient  means  of  application.  The  procedure  in  such  cases 
is  the  same  as  that  above  directed. 

Volatile  matters  can  in  this  way  be  recognized  by  their  odor 
emitted  at  boiling  temperature,  or  else  by  the  taste  which  they 
impart  to  the  liquid,  or  by  some  other  characteristic  test. 


420  MEANS   OF  FACILITATING   SOLUTION. 

The  solubility  of  a  solid  body  may  be  quantitatively  determined 
by  measuring  out  a  given  volume  of  the  solvent  liquid,  and  adding 
to  it,  while  boiling,  a  weighed  portion  of  the  substance  in  ques- 
tion. After  the  liquid  has  perfectly  cooled,  it  is  to  be  filtered 
upon  a  counterpoised  filter.  The  filter,  on  being  perfectly  dried 
in  vacuo  and  weighed,  will  give  the  insoluble  residue,  which,  de- 
ducted from  the  original  weight,  leaves  figures  that  express  the 
soluble  quantity. 

The  solubility  of  a  gas  may  be  ascertained  by  passing  up  a 
given  volume  of  water,  or  other  fluid,  the  solvent  power  of  which 
is  to  be  determined,  into  a  graduated  tube  filled  with  mercury 
and  inverted,  and  then  introducing  similarly  measured  volumes  of 
the  gas.  When  absorption  ceases,  by  bringing  the  interior  and 
exterior  levels  nearly  even,  allowing  for  the  small  column  of 
water,  the  remaining  gas  subtracted  from  the  whole  amount  in- 
troduced will  show  how  many  volumes  have  been  absorbed ;  and 
knowing  the  relative  sp.  gr.  of  the  gas  and  water,  the  volumes 
may  be  calculated  to  weights. 

1.  There  are  certain  conditions  which  greatly  facilitate  the 
solution  of  substances : — 1st,  comminution,  which  increases  the 
extent  of  surface ;    2d,  agitation,  which  promotes  the  frequent 
contact  of  all  parts  of  the  surface  with  fresh  portions  of  solvents ; 
3d,  the  freedom  from  impurity  of  both  the  solvent  and  body  to 
be  dissolved ;  4th,  it  is  also  influenced  by  the  quantity  and  state 
of  dilution  of  the  solvent ;  5th,  by  the  temperature ;  6th,  by  the 
mode  in  which  the  process  is  conducted. 

2.  Agitation  is  effected  by  stirring  with  glass  rods  when  the 
containing  vessel  is  open  at  the  top.     The  rod  should  be  rounded 
at  the  end  over  the  blowpipe  flame,  and  to  prevent  its  rolling 
from  the  table  or  top  of  the  vessel  upon  which  it  should  be  placed, 
may  be  square  instead  of  cylindrical  as  is  usual.     A  very  conve- 
nient and  effective  mode  of  bringing  all  portions  of  the  liquid 
successively  in  contact  with  the  substance  to  be  dissolved,  is  to 
place  the  latter  in  a  cullendered  diaphragm  suspended  beneath 
the  surface  of  the  liquid.    The  first  stratum  of  liquid  in  becoming 
saturated  increases  its  density,  and  consequently  descends  and 
displaces  a  lower  and  fresher  portion,  which,  being  in  the  same 
way  surcharged  in  its  turn,  gives  way  to  successive  strata,  and  so 
the  operation  continues  until  the  whole  of  the  matter,  or  so  much 


SOLUTION   OF   SOLIDS.  421 

as  can  be,  is  taken  up.  This  mode  keeps  the  substance  in  con- 
stant contact  with  new  portions  of  liquid,  and  is,  in  fact,  a  kind  of 
displacement  process. 

When  flasks  or  bottles  are  used  the  same  effect  may  be  pro- 
duced by  repeated  shaking. 

TRITURATION  in  a  mortar  and  alternate  decantation  and  fresh 
additions  of  the  solvent  greatly  facilitate  the  solution  of  solid 
substances. 

3.  The  purity  of  the  solvent  is  an  important  consideration,  for 
if  it  contain  foreign  matters,  they  may  impart  a  dissolving  power, 
which  is  not  inherent  in  the  pure  liquid,  or  diminish  that  already 
possessed  by  it.  Faraday  makes  the  following  excellent  remarks 
upon  this  subject. 

"It  is  necessary  that  the  student  be  on  his  guard  respecting 
certain  variations  in  the  solubility  of  bodies,  arising  from  the  pre- 
sence of  other  matters.  He  will  continually  find  that  small 
portions  of  substances  generally  considered  as  insoluble  in  water 
will  remain  in  neutral  solutions  when  some  other  substance  is 
present,  or  because  of  slight  mutual  decomposition ;  and  he  will 
also  frequently  find  that  matter  usually  considered  as  readily 
soluble,  is  so  with  difficulty  when  in  contact  with  substances  with 
which  it  is  not  apparently  in  combination.  Thus  water  boiled 
upon  muriate  of  potash  and  phosphate  of  baryta  will  be  found  to 
contain  more  baryta  than  if  boiled  alone  upon  the  phosphate ; 
and,  on  the  contrary,  if  oxide  of  iron  and  alumina  be  precipitated 
together  from  a  solution,  it  will  be  found  much  more  difficult  to 
dissolve  the  alumina  by  solution  of  potash  than  if  it  had  been 
thrown  down  alone. 

"  The  alkaline  earths  are  remarkably  soluble  in  solutions  of 
sugar,  and  also,  though  to  a  less  degree,  in  solutions  of  extractive 
and  other  vegetable  matters ;  hence  they  are  retained  in  solution 
at  times  in  very  unexpected  situations,  and  might  give  rise  to 
much  uncertainty  in  the  appearances  and  characters  of  other 
substances,  unless  the  experimenter  were  aware  of  the  general 
fact.  Platina  is  not  itself  soluble  in  nitric  acid,  even  when 
spongy  and  in  its  most  comminuted  form,  but  when  alloyed  in 
small  quantities  with  metals  dissolved  by  that  acid,  it  becomes 
soluble  with  them,  and  in  consequence  appears  now  and  then  in 
situations  where  it  is  not  expected.  Tartaric  acid  or  tartrates 


422  INFLUENCE  OF  TEMPERATURE. 

have  an  extraordinary  power  in  rendering  many  metallic  oxides 
soluble,  which  are  not  so  by  other  acids  without  it ;  and  still 
more  in  holding  them  in  solution  when  such  substances  are  added 
as  in  ordinary  circumstances  effect  their  separation.  The  oxides 
of  bismuth,  antimony,  tin,  and  titanium,  are  easily  dissolved  by 
acids  when  tartaric  acid  is  present ;  and  being  present,  ammonia 
no  longer  has  the  power,  upon  its  addition,  of  separating  the 
oxides  of  iron,  titanium,  manganese,  cerium,  cobalt,  nickel,  lead, 
antimony,  and  the  earths,  alumina,  magnesia,  and  yttria,  from 
their  solutions,  and  in  certain  cases  even  potash  or  soda  fails  so 
to  do.  Great  advantage  may  be  taken  of  this  property  occasion- 
ally, but  sometimes  it  is  equally  disadvantageous  in  preventing 
the  usual  action  of  reagents."1 

4.  In  regard  to  the  quantity  and  state  of  dilution  of  a  solvent, 
it  must  be  remembered  that  some  substances  require  more  of  it 
than  others  for  their  solution,  and  that  it  should  be  in  a  greater 
degree  of  dilution.     Therefore,  in  examining  the  solubility  of  a 
body  always  commence  with  small  quantities,  and  increase  both 
quantity  and  strength  gradually  as  may  be  required. 

5.  Temperature  exerts  a  considerable  influence  in  the  solution 
of  bodies;  and  though  in  a  few  instances,  as  in  the  solution  of 
lime,  magnesia,  and  anhydrous  sulphate  of  soda  in  water,  its 
elevation  impairs  the  power  of  the  solvent,  yet  as  an  almost  uni- 
versal rule  it  facilitates  its  action.     The  temperature  must  be 
adapted  to  the  nature  of  the  solvent  and  the  substance  to  be  dis- 
solved, and  of  the  solution  formed. 

It  may  be  as  well  to  mention  that  the  caloric  rendered  latent 
at  the  moment  of  the  liquefaction  of  a  solid,  which  is  being  dis- 
solved in  a  liquid,  causes  a  decrease  of  temperature.  Solution 
in  volatile  liquids  should  be  in  most  cases  performed  in  the  cold, 
and  when  of  small  quantities  in  narrow-necked  flasks.2  If  heat 
is  required,  especially  when  the  vapors  are  inflammable,  a  retort 
or  covered  still  must  be  used  ;  and  if  the  distillate  is  valuable,  a 
recipient  may  be  annexed  to  receive  as  much  as  comes  over. 

*  Annales  de  Chimie,  xxiii,  356. 

2  When  weighed  quantities  are  to  be  transferred  to  a  flask  or  other  narrow- 
mouthed  vessel,  the  use  of  a  barrel  will  prevent  liability  of  loss.  Any  particles 
that  may  adhere  to  the  side  of  the  funnel  can  be  washed  down  with  portions  of 
solvent. 


SOLUTION   OF  LIQUIDS. 


423 


Fig.  340. 


6.  The  mode  of  effecting  solution  varies  with  the  substance 
under  process :  MACERATION,  DECOCTION,  INFUSION,  DIGESTION, 
BOILING,  and  DISPLACEMENT,  have  each  and  all  appropriate 
application. 

In  ordinary  solution  the  solid  should  be  added  in  portions,  and 
a  sufficient  interval  allowed  for  the  solution  of  those  in  the  liquid 
before  fresh  are  added. 

The  containing  vessels  should  be  those  which  resist  the  action 
of  heat,  acid,  alkalies,  and  corrosive  liquids. 

For  solution  in  the  cold,  or  at  slightly  warm  temperatures,  jars 
of  hard  German  glass,  or  beaker  glasses,  Fig. 
340,  are  very  appropriate  vessels.  The  ma- 
terial in  powder  is  added  to  the  fluid  in  the 
jar,  and  contact  of  fresh  surfaces  promoted 
by  stirring  with  a  glass  rod.  If  the  liquid 
solvent  is  volatile,  a  glass-stoppered  bottle  is 
a  convenient  substitute  for  the  jar,  agitation 
being  effected  by  shaking  it  to  and  fro. 

Some  volatile  substances,  which  are  inso- 
luble in  water  under  ordinary  circumstances, 
are  taken  up  by  it  in  the  state  of  vapor.     For  this  purpose  both 
should  be  distilled  together. 

When  solutions,  emitting  corrosive  or  disagreeable  fumes,  are 
being  made  in  open  vessels,  the  operation  should  be  conducted 
under  a  hood,  the  barrel  of  which  connects  with  the  chimney-flue 
so  as  to  insure  their  exit. 

For  making  saturated  solutions  of  most  substances,  EBULLI- 
TION is  necessary.  For  this  purpose  the  solid  must  be  boiled  with 
the  solvent  until  the  latter,  on  cooling,  deposits  some  of  its 
charge.  The  cooled  solution  is  then  to  be  filtered. 

Metals  in  their  free  state  are  dissolved  one  in  the  other  by 
FUSION. 

Solution  of  Liquids. — Agitation  of  the  liquid  to  be  dissolved 
together  with  the  solvent  generally  effects  solution.  If  upon 
repose  there  are  two  layers,  then  all  the  matter  is  not  taken  up, 
and  that  portion  which  represents  the  solution  must  be  separated, 
and  a  fresh  quantity  of  the  solvent  added.  This  process  is  to 
be  repeated  until  all,  or  as  much  as  possible,  of  the  liquid  is 
dissolved. 


424  SOLUTION    OF   GASES. 

Solution  of  Gases. — The  generation  and  absorption  of  gases 
are  generally  simultaneous  processes,  and  have  been  fully  treated 
of  at  pp.  340-860.  When  water  is  used,  it  must  be  distilled  and 
boiled,  to  expel  air.  Viscid  liquids  are  not  less  solvent  than 
others,  but  take  up  the  gas  much  more  slowly.  As  a  general 
rule,  the  capacity  of  a  liquid  for  a  gas  is  proportional  to  its  rarity. 
(Berzelius.) 

Faraday  succeeded  (Ann.  de  Chim.  et  de  Pliys.  3d  Series, 
Vol.  13,  p.  121)  in  liquefying  certain  gases  by  the  combined  aid 
of  pressure  and  refrigeration,  among  them  olefiant  gas,  fluosi- 
licic  and  hydrochloric  acids.  Alcohol  was  partially  solidified  in 
the  same  manner.  Hydriodic,  hydrobromic,  and  carbonic  acids, 
sulphuretted  hydrogen,  and  ammonia,  assumed  well-defined  solid 
forms. 

The  author  thus  speaks  for  himself: — "I  sought,  in  the  first 
place,  to  obtain  a  very  low  temperature,  and  employed  for  this 
purpose  Thilorier's  bath  of  solid  carbonic  acid  and  ether,  placing 
it,  however,  under  the  recipient  of  an  air-pump.  The  bath  vessel 
was  an  earthenware  dish  of  four  cubic  inches  capacity,  and  fitted 
to  a  somewhat  larger  dish,  with  several  folds  of  dry  flannel  inter- 
vening. The  mixture  lasted  for  an  half  hour.  By  maintaining 
a  constant  vacuum,  I  lowered  the  temperature  to  such  a  degree, 
that  the  carbonic  acid  of  the  bath  was  not  more  volatile  than 
water  at  the  temperature  of  86°,  for  the  barometer  of  the  air- 
pump  stood  at  28*2  inches,  the  external  barometer  being  at  29-4. 

"  This  arrangement  made,  I  joined  together,  by  means  of  corks 
and  stop-cocks,  some  small  glass  and  copper  tubes,  so  that,  with 
the  aid  of  two  pumps,  I  was  able  to  subject  various  gases  to  a 
pressure  of  40  atmospheres,  and,  at  the  same  time,  to  submit 
them  to  the  intense  cold  obtained  under  the  air-pump,  and  to 
examine  the  resulting  effects.  As  I  expected,  the  cold  produced 
several  results  which  pressure  alone  would  never  have  done,  and 
principally  in  the  solidification  of  bodies  ordinarily  gaseous." 

The  two  pumps,  or  condensing  syringes,  used  by  Faraday, 
were  fixed  to  a  table,  "  the  first  having  a  piston  of  an  inch  dia- 
meter, and  the  second  one  of  only  half  that  size ;  and  both  were 
so  associated  by  a  connecting-pipe  that  the  first  pipe  forced  the 
gas  into  and  through  the  valves  of  the  second;  and  then  the 


SOLUTION   OF   GASES.  425 

second  could  be  employed  to  throw  forward  this  gas  already  con- 
densed to  ten  or  twenty  atmospheres,  into  its  final 
recipient,    the   condensing-tube,  at   a   much   higher 
pressure." 

The  condensing-tubes  were  of  green  bottle  glass, 
being  one-sixth  to  one-fourth  of  an  inch  external  dia- 
meter, and  from  one-forty-second  to'  one-thirtieth  of 
an  inch  in  thickness.  They  were  of  two  kinds,  about 
nine  and  eleven  inches  in  length ;  one  in  form  of  an 
inverted  syphon,  Fig.  341,  having  the  bend  cooled 
by  immersion  in  a  cold  bath ;  and  the  other,  hori- 
zontal, Fig.  342,  having  a  curve  downward,  near  one 
end,  to  be  cooled  in  the  same  manner.  Into  the 
longest  leg  of  the  syphon-tube,  and  the  straight  part  of  the  hori- 
zontal-tube, minute  pressure-guages  were  introduced  when  re- 
quired. The  caps,  stop-cocks,  and  connectors,  were  attached  to 

Fig.  342. 


I 


the  tubes  by  common  cement,  and  the  screw  joints  made  tight 
by  leaden  washers." 

The  following  table  (from  Gray's  Pharmacopoeia)  of  the 
solubility  of  some  of  the  salts  most  in  use  will  be  found  very 
convenient. 


*•''-. -4 


426 


SOLUBILITY  OF    SALTS. 


THE  SOLUBILITY  OF  SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

Alcohol 

at  60°              at  Boiling-point. 

at  60°         at  Boiling-point. 

ALUMINA. 

Acetate  of    . 

Undetermined. 

Arseniate  of 

Insoluble. 

Borate  of 

Uncrystallizable. 

Camphorate  of  . 

0-05. 

Lactate  of    . 

Uncrystallizable. 

Muriate  of 

Very  soluble 

100  at  54  i°. 

Nitrfcte  of    . 

Very  soluble 

ittW      100 

Oxalate  of 

Uncrystallizable, 

2-91 

Phosphate  of 

Insoluble. 

Seleniateof 

Insoluble. 

Sulphate  of  . 

50. 

Sulphate  of,  and  Potash 

5-4,        .            .     133-33 

Sulphate  of,  and  Soda 

100. 

Sulphite  of        *  - 

Insoluble. 

Tartrate  of  . 

Uncrystallizable, 

2-91. 

Tartrate  of,  and  Potash 

Uncrystallizable. 

Tungstate  of            , 

Insoluble. 

Urate  and  Lithate  of 

Insoluble. 

AMMONIA. 

Acetate  of    . 

Very  soluble, 

Readily  soluble. 

Arseniate  of 

Soluble. 

Binarseniate  of 

Soluble. 

Arsenite  of 

Uncrystallizable. 

Benzoate  of  . 

Soluble. 

Boletate  of 

38. 

8i,           .         '  . 

.      ir?°J  $  .'     0-416 

Camphorate  of  . 

1,      .         <  Lj!       .    33 

Carbonate  of  (Sesqui) 

33     (Ure). 
20     (Brands). 

Chlorate  of 

Very  soluble. 

Chromate  of 

Very  soluble. 

Citrate  of 
Ferrocyanide  of 

Difficultly  crystallizable. 
Very  soluble. 

J 

Formate  of 

Soluble. 

Hydriodate  of  (or  Iodide) 
of  Ammonium)          .     J 

Very  soluble. 

Hydrocyanate  of 

Soluble. 

Hydrosulphuret  of 
Hypophosphiie  of    . 

Very  deliquescent. 
Soluble  and  deliquescent. 

Hyposulphite  of 

Very  soluble. 

lodate  of 

Sparingly  soluble. 

Lactate  of 
Meconate  of 

Uncrystallizable. 
66. 

Molybdate  of    . 

Soluble. 

Muriate  of  (or  Chloride  of) 
Ammonium          .           J 

36,    .            .            .  100 

f                     ~    .             7 
j  7'5  at  80°  (  2  "  >     '900 
S  4-75     do.  <  ¥•£  >     '87-2 

1  1-5       do.   (£  «)     '834 

Nitrate  of 

50,          .            .         100 

.             .             .        19-16 

Oxalate  of    . 

4-5  .            .             40  84 

Phosphate  of                  . 

25     (Brajide). 

SOLUBILITY  OF   SALTS. 


427 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

Alcohol 

at  60°             at  Boiling-point. 

at  60°         at  Boiling-point. 

AMMONIA. 

Biphosphate  of 
Phosphite  of 

Less  soluble. 
Very  soluble. 

Purpurate  of 

•0066,          much  more. 

Pyrolithate  of    . 

Soluble. 

Suberate  of  . 

Very  soluble. 

•.  *   i 

Succinate  of 

Very  soluble. 

Sulphate  of  . 

50     (Branded             100 

Sulphite  of 

100     (Ure). 

Tartrate  of  . 

60-03         .            .  304-7 

2-91 

Tungstate  of 

Soluble. 

ANTIMONY. 

Acetate  of 

Soluble.    (Ure.) 

Benzoate  of  . 

Soluble.    (Ure.) 

Tartrate  of 

Very  soluble.  (Brands.) 

Potassio-tartrate  of  . 

7      .            .            .50 

BISMUTH. 

Acetate  of    .            . 

Soluble. 

Arseniate  of       .            . 

Insoluble. 

J 

Benzoate  of. 

Soluble, 

Sparingly. 

Carbonate  of,     . 

Insoluble. 

Chloride  of  . 

Deliquescent. 

Nitrate  of 

Decomposed. 

Phosphate  of 
Sulphate  of 

Soluble. 
Decomposed. 

BARYTA. 

5  at  50°,          10  at  212° 

Acetate  of    . 

88,      .            .            .  % 

Antimoniate  of  . 

Insoluble. 

Antimonite  of 

Slightly. 

Arseniate  of 

Insoluble. 

Arsenite  of  . 

Difficultly. 

Benzoate  of 

Soluble. 

Borate  of 

Very  sparingly. 

Camphorate  of  . 
Carbonate  of 

Very  sparingly. 
Very  nearly  insoluble. 

Chlorate  of 

25. 

Chromate  of 
Citrate  of 

Very  sparingly. 
Difficultly  soluble. 

Ferrocyanuret  of 

•0005.            .            .  '01 

Hydriodate  .of  (or  Iodide  < 
of  Barium)      .            .     | 

Very  soluble. 

Hydrosulphuret  of  . 
Hypophosphite  of 

11,     .           .           -  50 
Very  soluble. 

1  •£ 

lodate  of 

•33           .            .16 

Lactate  of 

Soluble. 

Lithate  of     . 

Insoluble. 

r\  at  80°  .1  «g    r  -900 

Muriate  of  (or  Chloride  of 

Qfi.ft                           68-5 

(0*9  .  aSjJ  ;848 

Barium)  (Anhydrous) 

ou  o   •              * 

\0-09    .'    JOT      I   -8" 

f  1  -56  at  80°  C       1     9°° 

0-43     .     •  p  »  1     '848 

Muriate  of  (or  Chloride  of 

43    (Brande),        .      78 

<^  0-32     .     X  6§  f  '834 

Barium)  Cryst.       .        ; 

0-06     .     •Lj'/2J 

428 


SOLUBILITY    OF   SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

Alcohol 

at  6j°            at  Boiling-point. 

at  60°         at  Boiling-point. 

BARYTA. 

5  at  50°           10  at  212° 

r~                                 ^ 
Nitrate  of     . 

$    8-  18  at    58-9°. 
I  35-18  at  214-97°. 

Oxalate  of 

Nearly  insoluble. 

Phosphate  of 

Insoluble. 

Phosphite  of                  . 

025. 

Pyrocitrate  of 

•066,            .               '02 

Sulphate  of 

Insoluble. 

Sulphite  of  . 

Insoluble. 

Tartrate  of 

Slightly. 

COBALT. 

Acetate  of    . 

Soluble. 

Antimoniate  of  . 

Soluble. 

Arseniate  of 

Insoluble. 

Borate  of 

Scarcely. 

Carbonate  of 

Insoluble. 

Lactate  of 

•026     (V  re.) 

Muriate,  or  Chloride  of 

Very  soluble. 

Nitrate  of 

Soluble,  . 

100  at  54  i°. 

Oxalate  of    . 

Insoluble. 

Sulphate  of 

4     (Brande), 

Insoluble. 

Tartrate  of  . 

Soluble. 

COPPER 

Acetate  of 

(Ure),    .        20 

Antimoniate  of 

Insoluble. 

Arseniate  of 

Insoluble. 

-~'\ 

Benzoate  of. 

Slightly. 

Borate  of 

Insoluble. 

Carbonate  of 

Insoluble. 

Chlorate  of 

Soluble. 

Chromate  of 

Insoluble. 

Citrate  of 

Insoluble. 

Ferrocyanide  of, 

Insoluble. 

Fluoride  of 

Soluble. 

Formate  of  , 

12. 

Hyposulphite  of 
Muriate,  or  Chloride  of 

Soluble. 
Soluble,  . 

100  at  176°. 

Dichloride  of 

Nearly  insoluble. 

Nitrate  of     . 

Deliquescent. 

Oxalate  of 

Soluble? 

and  Ammonia    . 

Soluble? 

and  Potassa 

Soluble  ? 

and  Soda 

Insoluble. 

Phosphate  of 

Insoluble. 

Subnitrate  of 

Insoluble. 

- 

Sulphate  of 

25,     ...            .  50 

Disulphate  of 

Insoluble. 

Trisulphate  of   . 

Insoluble. 

Sulphite  of  Protoxide, 
Sulphate  of,  and  Potassa 

Insoluble. 
Soluble. 

and  Ammonia 

Soluble. 

Ammonia  Subsulphate 
Tartrate  of,        .        :  j*  .' 

66-6. 
Soluble. 

Bitartrate  of                        . 

Less  soluble. 

Tartrate  of,  and  Potassa 

Soluble 

t:'  ' 

SOLUBILITY   OF  SALTS. 


429 


Name  of  Salt. 

Solubility  in  100  parts  Water 

Solubility  in  100  parts 
Alcohol 

at  60°           at  Boiling-point. 

at  60°         at  Boiling-point. 

GOLD. 

Perchloride  of 

Soluble. 

Protochloride  of 

Soluble. 

IRON. 

Acetate  (Prot.) 

Soluble. 

Acetate  (Per.)   . 

Uncrystallizable. 

Antimoniate  of 

Insoluble. 

Arseniate  of  (Prot.) 

Insoluble.    ,  > 

Arseniate  of  (Per.)  . 

Insoluble. 

Benzoate  of 

Insoluble. 

Borate  of 

Insoluble. 

Citrate  (Proto.)  . 

Soluble. 

Citrate  (Bi-proto.)   . 
Citrate  (Per.)     . 

Sparingly  soluble. 
£  Very  soluble   and  un-} 
(     crystallizable.              J 

Ferrocyanide(PrussianBlue 

Insoluble. 

Fluoride  of  . 

Insoluble. 

. 

Gallate  of  Peroxide  of  . 

Insoluble. 

Hyposulphite  of 

Soluble. 

Lactate  of  Protox.  of    . 

Scarcely. 

Molybdate  of  Protox.  of    . 

Insoluble. 

Protochloride  of 

Soluble. 

Perchloride  of 
Nitrate  of  Protoxide  of 
Nitrate  of  Peroxide  of 

Very  soluble,     . 
Uncrystallizable. 
Very  soluble. 

100  at  176°. 

Oxalate  of  Protoxide  of 

Soluble. 

Oxalate  of  Peroxide  of 

Scarcely. 

Phosphate  of 

Insoluble. 

Phosphate  of  Peroxide  of  . 

Nearly  insoluble. 

Superphosphate  of 
Succinate  of  Peroxide  of    . 

Nearly  insoluble. 
Insoluble. 

Sulphate  of  (Cryst.) 
Sulphate  of  (dry)      . 

76-238   (Brande),    333'3 

Persulphate  of  . 
Hyposulphite  of 

Uncrystallizable, 
Uncrystailizable. 

Soluble. 

Persulphate  of  and  Potassa 

Soluble. 

Persulphate  of  and  Am-) 
monia  .            .            .     j 

Soluble. 

Tartrate  (Proto.)  of 

0-25    (Dumas). 

Tartrate  (Per.)  of 

Soluble. 

Tartrate  of  and  Potassa 

Uncrystallizable, 

Soluble. 

LEAD. 

—                  A. 

Acetate  (Cryst.) 

27    (BostocJc),       .      29 

12'5.    (Brande.) 

Acetate  (Anhyd.)    . 
Diacetate  of 

Soluble.' 

Soluble. 

Antimoniate  of 

Insoluble. 

Arseniate  of 

Insoluble. 

Benzoate  of 

Insoluble. 

Borate  of 

Insoluble. 

Carbonate  of 

Insoluble. 

Citrate  of 

Nearly  insoluble. 

Chlorate  of  . 

Soluble. 

Chloride  of 

3-33    (Brande),     .    4'5 

Chloride  of  (fused). 

Chromate  of 

Insoluble. 

Ferrocyanuret  of     . 

Insoluble. 

Gallate  of 

Insoluble. 

Iodide  of 

0-08    .     .            .0-5 

Hyposulphite  of 

Soluble. 

430 


SOLUBILITY  OF   SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

j. 

Alcohol 

at  60°           at  Boiling-point. 

at  60°         at  Boiling-point. 

LEAD. 

Lactate  of    . 

Soluble.    (Ure.) 

Superlactate  of  . 

Soluble. 

Malate  of 

Scarcely. 

Molybdate  of     . 

Insoluble. 

Nitrate  of     . 

13. 

Dinitrate  of 

(  Scarcely  at  60°,  but  much 
(     more  so  at  212°. 

Oxalateof    . 

Insoluble. 

Phosphate  of 

Insoluble. 

Phosphite  of 
Succinate  of 

Insoluble. 
Insoluble. 

Sulphate  of  . 
Sulphite  of 

Not  absolutely  insoluble. 
Insoluble. 

Tannate  of  .            .            . 

Insoluble. 

Tartrate  of 

Almost  insoluble. 

and  Potassa 

Insoluble.     (Berzelius.) 

LIME. 

(Kirwan.) 

f2'4  at80°fo    ."|     -900 

Acetate  of  . 

Soluble,  .           .      ,?  ; 

J  4-12    .     J  £f  I   '848 

}  4-75    .     r\   *£•  f   -834 

(jl-88    .     .  L«2     J     '817 

Antimoniateof  . 

Insoluble. 

Arseniate  of 

Insoluble. 

Arsenite  of 

Difficultly  soluble. 

Benzoateof. 

Sparingly  soluble. 

Borate  of 

Very  difficultly. 

Carbonate  of  (Anhyd.) 
Chlorate  of 

Insoluble. 
Very  soluble,     . 

Soluble. 

Chromateof 

Soluble. 

Citrate  of 

Nearly  insoluble. 

Fluoride  of  ... 

Insoluble. 

Hypophosphite  of 

(Solubility  nearly  equal 
(     at  ail  temperatures. 

Hyposulphate  of 

40-65.     (Brande.)       150 

Hyposulphite  of 

Very  soluble. 

lodate  of 

20,              .     .       .     100 

Iodide  of  Calcium 

Deliquescent. 

Malate  of     . 

•66,             .            .1-53 

Molybdate  of     . 

Insoluble. 

.''; 

f200  at  32°. 

Muriate  (or  Chloride  of) 

J  400  at  60°. 

Calcium)         .           .     j 

1  almost  any  quantity  at 

220°. 

Nitrate  of     . 

25,           .       «N|J 

.     161-66 

Oxalate  of          .            . 

Insoluble. 

Phosphate  of 

Insoluble. 

Biphosphate  of  . 

Soluble. 

Subphosphate  of 

Almost  insoluble. 

Succinate  of 

Difficultly  soluble. 

Sulphate  of  . 

0-301  at  50°. 

Sulphite  of 

12-5. 

Tartrate  of  . 

5  Nearly  insoluble  at  60°, 
(     but  -16  at  212°. 

Tungstate  of     . 

Insoluble. 

LITHIA. 

Acetate  of    . 
Bicarbonate  of  .           . 

Deliquescent. 
Slightly  soluble. 

. 

SOLUBILITY   OF   SALTS. 


431 


Name  of  Salt. 

Solubility  in  100  parts  Water 

Solubiliiy  in  100  parts 
Alcohol 

at  60°           at  Boiling-point. 

at  60°         at  Boiling-point? 

LITHIA. 

Borate  of 

Soluble. 

Carbonate  of 

1,               ... 

Insoluble. 

Chloride  of  Lithium 

Very  deliquescent. 

Chromate  of 

Very  soluble. 

Citrate  of     . 
Nitrate  of                  «    . 
Oxalate  of    . 

Very  difficultly  soluble. 
Very  deliquescent. 
Very  deliquescent. 

Binoxalate  of     . 

Less  soluble. 

Phosphate  of 

Insoluble. 

Sulphate  of 

Soluble. 

Tartrate  of  . 

Easily  soluble. 

and  Potassa. 

Easily  soluble. 

and  Soda 

Easily  soluble. 

MAGNESIA. 

Acetate  of 

Very  soluble. 

Arseniate  of 

Deliquescent. 

Arsenite  of 
Benzoate  of  . 

Difficultly  soluble. 
Soluble. 

Borate  of 

Insoluble. 

Carbonate  of 

Very  slightly. 

Chlorate  of 

Very  soluble. 

f50,            .            .      547 

Chloride  of  Magnesium 

200    (Brande),   . 

1  50  at  80°  (  Sp.  gr.  )  .817 
1                 <      of      > 
1  21  25       (   Spts.  )  -900 

Chromate  of 

Very  soluble. 

Citrate  of     . 

Difficultly  soluble. 

Iodide  of  Magnesium 

Soluble. 

Malate  of 

3'6     (Brande). 

Molybdateof 

6-66           .           .    8-35 

(  Nearly  insoluble  in  pure 

Nitrate  of 

100, 

^     alcohol. 

(11  sp.gr.  -840. 

Oxalate  of  . 

Nearly  insoluble. 

Phosphate  of 

6-66. 

and  Ammonia 
Suceinate  of 

Sparingly  soluble. 
Uncrystallizable. 

Sulphate  of  (dry)      . 
Sulphate  of  (cryst.) 

33-192,    .            .    73-57 
68-042,    .            .  15071 

1  at  80°.     (Kirwan.) 

and  Ammonia  . 

Soluble. 

and  Potassa 

Soluble. 

and  Soda 

33-3. 

Sulphite  of 
and  Ammonia  . 

5. 
Difficultly  soluble. 

Tartrate  of 

Insoluble. 

Tungstate  of 

Soluble. 

MANGANESE. 

.A. 

Acetate  of 

3,            ... 

Soluble. 

Ammonio-chloride  of 

Soluble. 

Ammonio-sulphate  of   . 
Antimoniate  of 

Soluble. 
Moderately  soluble. 

Arseniate  of       . 

Insoluble. 

Benzoate  of  . 

Deliquescent   (Brande). 

Carbonate  of      .            . 

Insoluble. 

Chromate  of 
Nitrate  of 

Soluble. 
Very  soluble, 

Soluble. 

Oxalate  of  .           . 

Insoluble. 

432 


SOLUBILITY   OF   SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

A 

Alcohol 

at  60°           at  Boiling-point. 

at  60°         at  Boiling-point. 

MANGANESE. 

Phosphate  of      . 
Succinate  of        •   V 

Nearly  insoluble. 
1.     (Ure.) 

Sulphate  of 

31.     (Ure.) 

50.     (Brande.) 

Hyposulphate  of 
Sulphite  of 
Tungstate  of 

Deliquescent. 
Insoluble. 
Insoluble. 

MERCURY. 
J^ 

Acetate  of  (Prot.) 

016.     (Braconnot.) 

Acetate  of  (Per.)     . 

Readily  soluble. 

Arseniate  of 

Insoluble. 

Benzoate  of  . 

Insoluble. 

Borate  of 

Insoluble. 

Bichloride  of 

6'25     (Brande),        33'3 

42-6,      .            .     85-2 

C     10-74  at  50°. 

J  Sprts.  sp.  gr.  -915. 

\      43-66  at  50°. 
(JSprts.  sp.  gr.  -818. 

Chloride  of 

•00833  at  212°   (Dumas). 

(Graham.) 

Chromate  of            .            . 

Insoluble. 

Citrate  of 

Insoluble. 

(    > 

Bicyanuret  of           .  -^ 

54 

, 

Fluoride  of 

Soluble. 

Molybdate  of 
Nitrate  (Prot.)  . 

Very  sparingly. 
(Soluble  and  decomposed 
(     by  excess. 

Nitrate  of  (Per.)      . 

Do.                   do. 

Oxalate  of  (Proto.) 

Scarcely. 

Oxakteof(Per.)      . 

Insoluble. 

Sulphate  of  (Proto.) 

0'20            .            .    0'33 

Sulphate  of  (Per.)    . 

Decomposed. 

Sulphate  of  (Sub.)      "  .  , 

•005            .            .  0-33 

Tartrate  of  . 

Insoluble. 

and  Potassa. 

Soluble. 

NICKEL. 

Acetate  of   . 

Very  soluble. 

Arseniate  of 

Soluble.     (Ure.) 

Carbonate  of 

Insoluble. 

Chloride  of 

Soluble  in  hot  water. 

Nitrate  of  Protox.    . 

50,           ... 

Soluble. 

and  Ammonia 

Soluble. 

Oxalate  of 

Insoluble. 

Phosphate  of 

Nearly  insoluble. 

Sulphate  of 

33-3,        .            .  185-71 

and  Ammonia  . 

25. 

and  Potassa 

11  1. 

and  Iron 

Soluble.. 

Tartrate  of        .           i" 

Very  soluble. 

PLATINUM. 

Protochloride  ut       .            (, 

Soluble,             .            .  ( 

(Easily  soluble,  also  in 

Perchlunue  of    .            ,     j 

Soluble,             .           .  I 

I     Ether. 

Protochloride  of      .           ', 
and  Ammonium  i 

Soluble,             .       ,    . 

Insoluble. 

and  Potassium     . 

Soluble, 

Insoluble. 

and  Sodium   . 

Uncrystallizable, 

Very  soluble. 

SOLUBILITY   OF   SALTS. 


433 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

A 

Alcohol 

at  60°           at  Boiling-point. 

at  60°         at  Boiling-point. 

PLATINUM. 

Bichloride  of           .           ) 
and  Ammonium  J 

Very  sparingly. 

and  Potassium     . 

Very  sparingly. 

and  Sodium   . 

Soluble,. 

-  Soluble. 

and  Barium 

Soluble. 

Protonitrate  of  . 

Soluble. 

Pernitrate  of 

Soluble. 

Protosulphate  of 

Soluble. 

Persulphate  of 

Very  soluble,     . 

(Very  soluble,  also  in 
I     Ether. 

POTASSA. 

100, 

200 

Ammonia-oxalate  of     . 

Soluble. 

Ammonia-sulphate  of 

13. 

Ammonia-tartrate  of    . 

Very  soluble. 

Antimoniate  of 

Slightly. 

Antimonite  of    . 

Soluble. 

Arseniate  of 
Binarseniate  of  . 

Uncrystalli/able, 
18-86  at  40°, 

3-75. 
Insoluble. 

Arsenite  of  . 

Uncrystallizable. 

Benzoate  of 

Very  soluble. 

Bibenzoate  of 

10. 

Borate  of 

Soluble. 

Camphorate  of 

1,      .            .            .25 

Carbonate  of 

100. 

Bicarbonate  of 

25,   .            .            .    83 

Chlorate  of 

6-03,               60  at  1881° 

Chromate 

48,    .            .  extremely. 

Insoluble. 

Bichromate  of    . 

10,  .           much  more. 

Citrate  of 

Very  soluble. 

Columbate  of     . 

Uncrystallizable. 

Ferrocyanide  of 

33-3,            .            .    100 

' 

Iodide  of  Potassium 

143  at  65°  (G.  Lussac]. 

Sparingly. 

lodate  of 

7-14     (Brande). 

Molybdate  of     . 

Soluble. 

• 

f2'083            '_ 

Chloride  of  Potassium 
t 

(29-21  at    66-83°) 
1  59-26  at  229-28°  \ 

)  4-62  at  80°  (  o  »  )   -900 
1  1-66    .    .   <  &£?   >812 

LO'38    .     .   (CCM)   '834 

(  29-31  at    64°) 

Nitrate  of 

)  236  45  at  207°  > 
(285-      at  238°) 

2-083 

Oxalate  of    . 

(50    (Ure).           .              I 
)30     (Brande),    .              ) 

(2-76  at  80°    Sp.gr.  '900 
1  1        .        of  Sprts.  '872 

Binoxalate  of    . 

(10  Brande.)    (UrelOO.) 

Quadroxalate  of 
Phosphate  of     .            . 

66-66 
Difficultly  soluble. 

-^       2'91 

Diphosphate  of 

Soluble  in  hot  water. 

Biphosphate  of  . 
Hypophosphite  of    . 

Hyposulphate  of 

Very  soluble. 
Very  deliquescent, 
(Difficultly  soluble  at  60°, 
\     readily  at  212°. 

Very  soluble. 

Hyposulphite  of 
and  Silver 

Deliquescent. 
Difficultly. 

Succinate  of 

Very  soluble. 

Sulphate  of 

(10-57  at    54°. 
J2633at2l4  . 

Bisulphate  of 

(  50  at    40°. 
1  200  at  220°. 

28 

434 


SOLUBILITY   OF    SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Name  of  Salt. 

A 

Alcohol 

at  60°            at  Boiling-point. 

at  60°         at  Boiling-point. 

POTASSA. 

Sulphite  of 

100. 

Tartrate  of  . 

100, 

0-416 

Bitartrate  of 

1-05,        .            .      6-66 

2-91 

Tartrovinate  of 

10,           .  any  quantity. 

«. 

Tungstate  of 
Nitro-tungstate  of  . 

Uncrystallizable. 
(ZTre),    5 

. 

SILVER. 

Acetate  of    . 

Very  difficultly  soluble. 

' 

Arseniate  of 

Insoluble. 

Arsenite  of  . 

Insoluble. 

Borate  of 

Difficultly  soluble. 

Chlorate  of  . 

25     (Chenemx). 

Chromate  of 

Very  slightly. 

Citrate  of     . 

Insoluble. 

Molybdate  of     . 

Insoluble. 

Chloride  of  (Fused) 

Insoluble. 

Nitrate  of  (Cryst.) 

100,            .            .    200 

25 

Oxalate  of    . 

Insoluble. 

Phosphate  of     . 

Insoluble. 

Succinate  of 

Soluble. 

Sulphate  of 

1-15. 

Sulphite  of  . 

Very  little  soluble. 

Hyposulphite  of 
and  Potassa 
Tartrate  of 

Soluble. 
Difficultly  soluble. 
Soluble. 

and  Potassa 

Soluble. 

SODA. 

Acetate  of    . 

35,            .            .       150 

Arseniate  of 

(10    (Thompson). 
{25     (lire-). 

Binarseniate  of 

Soluble. 

and  Potassa 

Soluble. 

Benzoate  of  . 

Very  soluble. 

Biborate  of 

8-033,       .            .        50 

Carbonate  of 

50,            .             .       100 

Bicarbonate  of  . 

7-6. 

Chlorate  of  . 

33-3,         . 

Sol.  in  sp.  rect. 

Chromate  of 

Very  soluble, 

Sparingly. 

Citrate  of     . 

100  or  more     (Brande). 

Iodide  of  Sodium 

173. 

lodate  of 

7'3, 

Insoluble. 

Molybdate  of     . 
Muriate  of  (or  Chloride  of  ) 
Sodium,          .           .     5 

Soluble. 
Equally  soluble   at  all) 
temperatures.  (Berz.'i) 
C  33-3  at    60°)       n 

(5  -8  at  80°  (Sp.gr.)  '900 
{  3'6     .     .  <     of    >  -872 
{0'5     .     .    (  Spts.  J  -834 

100     at  123°}      Duma*' 

50     af  60°        Berzel. 

C                                  '958 

Nitrate  of    . 

73     at    32°)      (Gay 
<  173     at  212°j    Lussac). 
80     at    32°  1 

j  10-5  at  80°  (Sp.gr.)  -900 
1  6    .    .    .  <     Of    >  '872 

LO-38    .     .  (  Spts.  )  -834 

22-7  at    50°  i    ^ 

55     at    61°  f  marx' 

J218-5  at  246°J 

Oxalate  of          .       .  .... 
Phosphate  of 

Sparingly  soluble. 
25,           .            .         50 

and  Ammonia 

Soluble. 

Biphosphate  of       J. 

Very  soluble. 

SOLUBILITY  OF   SALTS. 


435 


Name  of  Salt. 

Solubility  in  100  parts  Water 

Solubility  i  n  100  parts 
Alcohol 

at  60°           at  Boiling-point. 

at  60°        at  Boiling-point. 

SODA. 

Hypophosphite  of 
Succinate  of 

Very  soluble,     . 
Soluble. 

Very  soluble. 

Sulphate  of  (Cryst.) 

C  48-28  at  64°. 
1  322-  12  at  91°. 

(  16-73  at    64°)       ,n 

Sulphate  of  (dry)      . 

Hyposulphate  of 
Bisulphate  of 

<  50*65  at    91°  >      ^ay 
(42  -65  at  2  17°)    Lussac}' 
41-6,            .           .     91 
50. 

Insoluble. 
Insoluble. 

Sulphate  of,  and  Ammonia 

Soluble. 

Sulphite  of  . 
Hyposulphite  of 
Tartrate  of  . 

25. 
Deliquescent.     . 
56-37    (Thomson), 

Insoluble. 
Insoluble. 

and  Potassa". 

20. 

'Sol.  in   sp.   rect.,   but 

Tartrovinate  of 

Soluble,  . 

sparingly  in  absolute 

[     alcohol. 

Tungstate  of 

25,          .            .         50 

STRONTIA. 

<  0-625  at  60°)     (U    } 

^/^ 

1*1  Rt  212o       (      v^re;. 

Hydrate  of  . 
Acetate  of 
Arseniate  of 
Arsenite  of 

2*                          .          50 
Very  soluble. 
Sparingly  soluble. 
Sparingly  soluble. 

Borate  of 

0-76. 

Carbonate  of 

0-0651  at  212°. 

Chlorate  of 

Very  soluble.     . 

Soluble. 

Chloride  of  Strontium  . 

50, 

Soluble. 

Chromate  of 

Insoluble    (Brande). 

Citrate  of 

Soluble. 

Ferrocyanuret  of     . 
Iodide  of  Strontium 

25. 

Soluble. 

lodate  of 

25. 

Nitrate  of 

113 

Oxalate  of    . 

0-52 

Phosphate  of                  . 

Insoluble. 

Phosphite  of 
Hypophosphite  of 

Soluble. 
Very  soluble. 

Succinate  of             .            . 

Soluble. 

Sulphate  of 
Hyposulphite  of 

0-026  at  212°. 
20    (Gay  Lussac), 

Insoluble. 

Hyposulphate  of 
Tartrate  of  . 

22-22       .            •    66'66 
0-67  at  170o. 

TIN. 

Acetate  of 

Soluble. 

Arseniate  of 

Insoluble. 

Borate  of 
Nitrate  Proto.  of     . 

Insoluble. 
Uncrystallizable. 

Nitrate  Per.  of  . 

Scarcely. 

Oxalate  of    . 

Soluble. 

Phosphate  of     . 
Succinate  of 
Sulphate  Proto.  of 
Sulphate  Per.  of 
Tartrate  of        . 
and  Potassa 

Insoluble. 
Soluble. 
Crystallizable. 
Uncrystallizable. 
Soluble. 
Very  soluble. 

436 


SOLUBILITY   OF   SALTS. 


Solubility  in  100  parts  Water 

Solubility  in  100  parts 

Alcohol 

Name  of  Salt. 

vv 

at  60°            at  Boiling-point. 

at  60°         at  Boiling-point. 

ZINC. 

w 

Acetate  of 

Very  soluble. 

Antimoniate  of 

Very  sparingly. 

Borate  of 

Insoluble. 

Chromate  of 
Citrate  of 

Sparingly. 
Scarcely. 

Chlorate  of  . 
Chloride  of 

Very  soluble. 
Very  soluble.     . 

100  at  54i°. 

Iodide  of 

Soluble. 

lodate  of 

Difficultly  soluble. 

Lactate  of    . 

2     (Ure). 

Nitrate  of 

Deliquescent. 

Molybdateof 

Insoluble. 

Oxalate  of 

Nearly  insoluble. 

Phosphate  of 
Succinate  of 

Uncrystallizable. 
Soluble. 

Sulphate  of  . 

140    (Dumas). 

Sulphite  of 

81-81  at  220°,      . 

Insoluble. 

Hyposulphite  of 
Sulphate  of,  and  Nickel 
Tartrate  of  . 

Soluble,  . 
33-33. 
Difficultly  soluble. 

Soluble. 

Tartrovinate  of  . 
Trisulphate  of 

Soluble,  . 
Soluble. 

Sparingly  soluble. 

ACID. 

Arsenious 

Vitreous 

1-78  (Graham),      9'68 

Opaque 

2'9     (Graham),    11  '47 

Benzoic 

•50. 

Boracic  .            .            . 

3-9,      .          v     33-3 

20  at  176°    (Henry). 

Citric 

13333,    .            .     200 

Soluble. 

Gallic     . 

5,          .            .       33-33 

Oxalic  (Cryst.) 

11-5. 

Succinate  (Cryst.) 

4,         .            .      33-33 

74  at  176°. 

Tartaric 

150     (Brande),           200 

Soluble. 

Brucia 

•1177,      .            .        0-2 

Soluble. 

Cinchonia     . 
Morphia 
Quinia 

Insoluble,           .         0'04 
Nearly  insoluble,       1 
Nearly  insoluble,       0'5 

Partially  soluble. 
Very  soluble. 

Strychnia 

0'04     (Graham),          0'15 

$  5'  sp.  gr.   of  spts.    870 
I     (Duflos). 

Camphor 

0229,       . 

75  at  176°. 

Cane  Sugar 

200. 

MACERATION.— INFUSION.  437 


CHAPTER  XXI. 

MACERATION — INFUSION — DECOCTION — DIGESTION — BOILING — 
DISPLACEMENT. 

MACERATION. — The  soaking  or  steeping  of  a  substance  in  a 
liquid,  at  the  ordinary  temperature,  is  termed  maceration.  It  is 
almost  exclusively  applicable  to  organic  substances,  being  most 
frequently  resorted  to  as  a  means  of  hastening  and  facilitating 
the  after-solution  of  the  extractive  parts  of  hard,  compact,  or 
impervious  wood,  roots,  stems,  and  leaves,  by  the  more  active 
methods  of  DISPLACEMENT  or  of  EBULLITION.  It  is  employed 
when  the  soluble  principles  are  alterable  by  heat ;  and  is  also 
made  use  of  to  effect  the  solution  of  a  substance  containing 
several  principles,  the  solubility  of  which  varies  with  the  tempe- 
rature applied,  as  it  leaves  those  which  are  not  taken  up  in  the 
cold  to  be  acted  upon  by  the  aid  of  heat  in  a  subsequent  opera- 
tion. Thus,  for  example,  in  the  treatment  of  most  vegetable 
substances,  starch,  which  is  generally  present  and  is  only  soluble 
at  the  boiling-point  of  water,  will  remain  untouched,  while  all 
other  principles  soluble  without  heat  can  be  separated  from  it. 

The  mode  of  performing  the  process  is  merely  to  place  together, 
in  a  vessel,  the  solvent  and  the  substance  to 
be  dissolved,  and  to  allow  them  to  remain  a 
longer  or  shorter  time,  according  to  the  na- 
ture of  the  substance.  For  ordinary  purposes, 
a  loosely  covered  pan  of  blue  stoneware  is 
very  convenient.  In  delicate  operations,  a 
beaker-glass,  Fig.  340,  or  solution  jar,  Fig. 
343,  is  more  appropriate.  When  the  solvent 
is  volatile,  a  wide-mouthed  stoppered  bottle 
may  be  used. 

INFUSION. — This  process  is  likewise  appli- 
cable almost  solely  to  organic  substances. 
Instead,  however,  of  the  solid  remaining  in  contact  for  a  length 
of  time  with  the  solvent,  the  latter  is  first  heated  to  boiling  and 
then  poured  upon  the  former.  After  having  cooled,  the  liquid 
may  be  decanted  or  pressed  out. 


438 


DECOCTION. 


This  mode  is  used  for  the  exhaustion  of  flowers,  leaves,  roots, 
seeds,  and  other  substances  of  delicate  texture,  which  are  easily 
penetrable  and  readily  yield  their  soluble  matters ;  and  especially 
for  the  purpose  of  extracting  volatile  ingredients.  The  heat 
applied  to  the  solvent  increases  its  energy ;  but  as  the  material  is 
only  in  contact  for  a  limited  time,  the  interval  between  the  com- 
mencement and  completion  of  the  operation  is  not  sufficient  to 
affect  the  material  or  solution,  even  though  one  or  more  of  its 
components  are  alterable  by  heat. 

For  small  operations,  a  beaker  glass  covered  with  a  capsule,  or 
a  yellow  earthenware  stew-pan  with  lip  and.  cover,  such  as  can  be 
had  at  the  crockery  shops,  are  admirably  adapted.  In  larger 
pharmaceutical  processes,  a  special  apparatus,  Fig.  344,  is  em- 
Fig.  344. 


ployed.  It  is  known  as  Alsop  and  Squire's  Infusion  Pot,  and 
consists  of  three  pieces,  an  outer  pitcher  form  vessel  A,  an  inner 
perforated  bowl  B,  and  a  cover  c.  Its  material  is  generally  white 
stoneware  or  porcelain,  but  it  may  also  be  made  of  metal.  The 
inner  bowl  serves  as  a  support  for  the  solid  matters  to  be  infused, 
and  retains  them,  during  the  treatment,  in  constant  contact  with 
the  liquor  in  the  outer  vessel.  After  the  action  is  completed,  it 
is  only  necessary  to  remove  the  cover  and  lift  out  the  cullendered 
bowl;  for  the  infusion  is  clear  and  ready  for  use  without  the 
necessity  of  filtration. 

DECOCTION. — This  mode  of  solution,  which  is  so  important  to 
the  Pharmaceutist,  is  chiefly  employed  for  the  purpose  of  ex- 
hausting those  vegetable  substances,  which  will  not  readily  yield 
their  soluble  matters  to  water.  It  is  merely  an  extension  of  the 


SOLUTION  BY  DIGESTION.  439 

last  process,  and  consists  in  boiling  the  material  to  be  dissolved 
with  a  hot  solvent  in  a  covered  vessel,  or  saucepan,  until  all 
soluble  matter  is  taken  up.  Most  volatile  matters  are  expelled 
by  decoction;  but  those  which  are  insoluble,  save  by  prolonged 
action  of  heat,  are  dissolved  or  suspended,  as  it  were,  by  favor  of 
other  principles  present. 

Decoction  is  only  used  with  liquid  solvents  which  are  not 
decomposable  by  heat. 

In  all  of  the  preceding  processes,  as  well  also  in  others  in 
which  solid  vegetable  matter  is  subjected  to  the  solvent  action  of 
liquids,  the  calendered  ladle,  Fig.  345,  of  tinned  wire,  is  most 


Fig.  345. 


useful  for  transferring  the  residue  to  the  press,  for  removal  of 
any  retained  liquid. 

DIGESTION. — This  mode  of  solution  differs  from  maceration  in 
requiring  the  assistance  of  heat,  and  consists  in  exposing  a  body 
to  the  prolonged  action  of  a  liquid  in  a  covered  vessel,  at  any 
temperature  between  90°  F.  and  several  degrees  less  than  the 
boiling-point  of  the  solvent.  The  method  of  heating  varies  with 
circumstances,  and  can  be,  by  a  gentle  fire,  or  by  the  sand, 
steam,  water,  or  saline  Bath,  as  the  nature  of  the  operation 
may  require. 

In  analysis,  glass  or  platinum  vessels  are  used ;  but  in  less  im- 
portant operations,  those  of  other  materials  are  more  convenient 
and  economical. 

A  very  important  advantage  of  digestion  is,  that  it  allows  the 
perfect  solution  of  all  soluble  portions  of  a  substance,  without 
modifying  the  nature  of  the  solvent.  It  is  especially  useful  for 
the  decomposition  of  ores,  minerals,  and  other  substances  diffi- 
cultly acted  upon  by  acids  or  other  solvents,  and  also  for  effect- 
ing the  synthesis  of  compounds  requiring  a  long-continued  heat. 
Moreover,  it  is  very  available  in  preparing  alcoholic  and  aqueous 
solutions,  medicinal  oils,  and  other  pharmaceutical  products. 

In  analytic  operations,  digestion  is  performed  in  beaker  glasses. 


440 


SOLUTION    BY   DIGESTION. 


Fig.  346. 


These  are  bell-shaped  vessels,  Fig.  346,  of  Bohemian  glass,  and 
uniformly  thin  throughout,  so  as  to  support  a  considerable  eleva- 
tion of  temperature.  The  glass  must  be  well 
annealed,  hard,  and  free  from  lead,  so  as  to 
resist  the  action  of  acids.  These  vessels  come 
in  nests  of  different  numbers.  Their  size 
varies  gradually  upwards  from  an  ounce  in 
capacity  to  a  gallon. 

The  substance  to  be  acted  upon,  in  a  state 
of  fine  powder,  is  transferred  to  the  glass, 
which  must  be  perfectly  clean,  and  is  then 
mixed  with  the  proper  quantity  of  acid  or 
other  liquid  by  shaking  the  glass  after  the  addition,  or  by  the 
use  of  a  glass  stirrer,  taking  care,  however,  in  this  last  instance, 
if  for  analysis,  to  wash  off  adhering  particles  previous  to  its  with- 
drawal, with  a  little  fresh  solvent.  The  glass  is  then  to  be 
covered  with  a  square  of  window-glass  (free  from  lead),  a  porce- 
lain capsule,  or  watch-glass,  whichever  is  most  convenient,  so  that 
the  volatilized  vapors  condensing  upon  its  bottom  may  fall  back 
again  into  the  vessel. 

If  the  glass  is  small,  it  may  be  directly  heated  over  the  lowered 
flame  of  a  gas  or  spirit-lamp,  Figs.  40,  41, 
cautiously  and  gradually  heightened  as  the 
glass  becomes  heated.  To  modify  the  action 
of  the  flame  and  diminish  the  danger  of  frac- 
ture of  the  glass,  a  fine  wire  gauze  5,  for  the 
diffusion  of  the  heat,  may  be  interposed  be- 
tween its  bottom  and  the  flame.  Fig.  347 
•  represents  a  digestion  in  a  beaker  glass  a, 
over  a  gas  lamp  c.  For  larger  vessels  a  SAND- 
BATH  must  be  used. 

Thin  flat-bottomed  flasks,  with  narrow 
necks  and  ,  smooth  tops,  Fig.  348,  made  of 
hard  glass,  free  from  lead,  are  sold  especially 
for  this  purpose ;  but  the  common  sweet  oil 
or  Florence  flasks  are  much  more  economical 
and  equally  convenient  for  operations  adapted  to  their  capacity. 


DIGESTION   UNDER   PRESSURE.  441 

When  it  is  important  that  not  even  a  drop  of  substance  shall  be 
lost,  as  in  analytic  operations,  the  digesting  flask  should  have  the 
form  shown  in  Fig.  349.  The  body  is  pear-shaped,  with  a  flat 


Fig.  348.  Fig.  349. 


bottom,  and  gradually  tapers  towards  the  mouth,  which  is  lipped 
to  facilitate  the  pouring  of  the  contents. 

Digestion  on  a  small  scale  with  inflammable  liquids,  must 
always  be  effected  by  the  sand-bath,  so  as  to  avoid  danger  of 
explosion  from  ignition  of  vaporized  particles.  The  sand-bath 
may  then  be  heated  over  the  lamp,  as  at  Fig.  155 ;  and  in  large 
operations  by  the  small  charcoal  furnace,  as  at  Fig.  124. 

A  digestion  apparatus,  of  Berlin  porcelain,  adapted  for  a  water- 
bath,  is  shown  in  Fig.  350.  Its  dimensions 
are  7  inches  in  height,  and  4  inches  in  dia- 
meter, the  capacity  being  about  40  ounces. 
The  projection  b  is  a  flange  for  its  support 
in  the  bath ;  a,  the  socket  for  a  wooden 
handle,  and  (?,  a  section  of  the  cover. 
These  vessels,  made  also  of  other  sizes,  are 
very  convenient  in  pharmaceutical  opera- 
tions, for  the  digestion  of  organic  matters, 
especially  those  of  vegetable  origin. 

Digestion  under  Pressure. — The  solvent  power  of  water  may 
be  greatly  increased  by  presenting  it  to  the  substance  in  the  state 
of  vapor.  This  property  affords  the  advantage  of  making  aqueous 
solutions  of  highly  obstinate  substances.  The  appropriate  appa- 
ratus is  termed  a  digester.  That  which  Papin  used  for  exhausting 
bones  of  their  gelatin,  Fig.  351,  consisted  of  a  strong,  cylindrical, 
iron  or  copper  vessel,  with  sides  sufficiently  thick  to  resist 


442 


SOLUTION. 


Fig.  351. 


a  considerable  degree  of  pressure.  The  cover,  made  to  fit 
closely  to  the  body,  is  fastened  down 
by  a  screw  s.  There  are  two  openings  in 
it,  one  for  the  stop-cock  c,  and  the  other 
for  the  safety-valve  v,  with  its  weight 
I  w,  by  which  it  can  be  loaded  so  as  to 
resist  a  pressure  within  of  40  to  50  at- 
mospheres, if  necessary.  The  arrange- 
ment of  the  valve  is  shown  in  the  broken 
part  of  the  drawing.  The  steam  accu- 
mulating in  the  upper  part  of  the  body, 
when  matters  are  under  treatment,  being 
confined  by  the  loaded  valve  and  unable  to 
escape,  exerts  a  great  pressure  upon  the 

liquid  mixture  beneath,  and  thus  allows  it  to  be  raised  to  a  very  high 
degree  of  heat  without  boiling.  The  stop-cock  c  is  convenient  as 
a  try-cock,  for  making  examinations  during  the  progress  of  the 
experiments.  The  lever  regulates  the  pressure  in  proportion  to 
the  weight  placed  upon  it. 

In  large  operations,  D'Arcet's  apparatus  (see  Encyclopaedia  of 

Fig.  352.  Fig.  353. 


Chemistry,  article  GELATIN)  is  much  used.  It  is  shown  in  Figs. 
352  and  353.  Our  description  rjefers  to  the  extraction  of  gelatin 
from  bones  by  water  in  a  state  of  tense  vaporization. 


D'ARCET'S  DIGESTER.  443 

Fig.  352  is  a  vertical   section   of  the  apparatus.     A  is  an 
hermetically  closed  cast-iron  cylinder,  into  which  the  steam  is 
conducted ;  a  the  main  steam-pipe ;  b  a  vertical  pipe  conveying 
the  steam  into  the  cylinder  A ;  c  c  hranch-pipes  leading  the  steam 
to  the  bottom  of  the  cylinder;  d  a  stop-cock  upon  the  pipe  5,  for 
regulating  the  entrance  of  the  steam  into  the  interior  of  the 
cylinder.    (The  tubes  and  the  cylinder  should  be  wrapped  around 
with  woollens,  so  as  to  retain  their  heat  and  prevent  their  cool- 
ing.)    e  is  the  stop-cock  for  the  discharge  of  the  gelatinous  solu- 
tion ;  /  the  cover  of  the  cylinder,  which  is  fastened  to  the  cylin- 
der, so  as  to  prevent  the  escape  of  any  of  its  contents;  g  a 
tubulure  in  the  cover  for  the  reception  of  a  thermometer ;  h  a  tub 
to  receive  the  solution  as  it  is  formed ;  i  a  gutter  for  conveying 
into  another  vessel  the  grease  which  is  run  off  in  the  commence- 
ment of  the  operation;  K  another  gutter,  moving  on  a  pivot, 
which  receives  the  liquid  as  it  runs  from  the  cock  e,  and  empties 
it  into  the  tub  A,  or  into  the  trench  i ;  I  a  tube  for  feeding  the 
interior  of  the  cylinder  with  fresh  water ;  m  a  movable  adjust- 
ment attached  to  the  pipe  I  for  regulating  the  quantity  of  water 
and  preventing  a  too  great  elevation  of  temperature  in  the  inte- 
rior of  the  apparatus. 

Fig.  353,  elevation  of  the  interior  basket,  made  of  wire-cloth. 
This  basket,  or  cage,  receives  the  cleansed  and  crushed  bones, 
and  is  enclosed  in  the  cylinder  A ;  a  is  the  handle  with  which,  by 
means  of  a  pulley,  it  is  lifted  or  lowered,  to  be  emptied  or  charged. 
Four  or  more  of  these  machines  make  a  series,  and  the  boiler 
which  feeds  them  with  steam  should  carry  a  pressure  of  4  Ibs.  to 
the  inch. 

When  volatile  or  costly  liquids  are  used  as  solvents  in  digest- 
ing processes,  it  is  necessary,  both  on  the  score  of  economy  and 
of  the  efficacy  of  the  process,  to  use  certain  precautions.  In 
making  pharmaceutical  preparations  with  alcohol  or  ether,  for 
example,  it  must  be  remembered  that  these  liquids  volatilize  by  a 
high  heat,  and  unless  the  vaporized  particles  are  by  a  suitable 
arrangement  condensed  and  returned  to  renew  action  upon  the 
substance,  the  latter  will  be  evaporated  to  dryness  long  before 
sufficient  time  has  elapsed  for  the  completion  of  its  solution.  For 
this  purpose  an  ordinary  cooling-worm  may  be  attached,  as  shown 
in  Fig.  354.  The  vapors  escaping  from  the  digesting  vessel  a, 


444 


SOLUTION. 


are  condensed  partly  in  the  inclined  tube  6,  and  partly  in  the 
worm  c,  and  fall  back  again  into  the  flask  as  soon  as  they  become 
liquefied  by  the  water  surrounding  the  worm.  This  arrangement 
allows  a  prolonged  contact  of  solids  and  volatile  liquids,  without 
loss  or  alteration  of  the  latter, — a  very  important  consideration, 
as  time  is  an  influential  adjunct  in  digestion. 


Fig.  354. 


Fig.  355. 


Mohr  improves  upon  the  above  apparatus,  by  giving  it  the 
form  exhibited  in  Fig.  355.  It  consists  of  a  tin  plate  cylinder 
A,  tubulated  at  its  bottom.  Through  this  tubulure  passes  a  glass 


SOLUTION   BY  BOILING. 

tube  1 1,  adjusted  by  perforated  corks  to  the  tubulures  of  both 
cylinder  and  digesting  vessel  M.  The  vaporized  matter,  ascend- 
ing from  the  heating  vessel  M,  is  cooled  by  the  water  in  the 
cylinder,  and  which  surrounds  the  tube  1 1.  The  long-barrelled, 
tin  plate  funnel  T,  receives  the  amount  of  water  freshly  added, 
and  conveys  it  to  the  bottom  to  displace  that  which  has  become 
heated,  and  which  by  its  less  density  rises  to  make  its  escape 
through  the  outlet  A. 

SOLUTION  BY  BOILING. — This  mode  is  resorted  to  when  a  sub- 
stance can  only  be  exhausted  of  its  soluble  portion  at  the  boiling- 
point  of  the  solvent.  The  exact  point  of  temperature  at  which  a 
liquid  boils,  depends  partly  upon  the  amount  and  fluctuations  of 
pressure,  and  the  nature  and  construction  of  the  vessel.  When 
the  pressure  of  supernatant  vapor  is  removed  by  uncovering  the 
vessel,  ebullition  is  facilitated  and  takes  place  at  lower  tempera- 
tures. Indentation  or  roughening  of  the  surface  of  the  heating 
vessel,  or  any  other  means  by  which  the  heating  surface  is  in- 
creased, and  escape  of  gaseous  matter  is  promoted,  lowers  the 
boiling-point  of  a  liquid.  For  this  latter  reason,  platinum  scraps 
or  pieces  of  unglazed  card,  or  of  cork,  pacify  turbulent  ebullition 
and  render  the  process  tranquil  and  uniform. 

The  heat  applied  should  never  exceed  the  degree  at  which  the 
solvent  boils,  especially  in  metallic  vessels,  otherwise  ebullition 
is  retarded,  for  beyond  a  certain  temperature  a  repulsion  between 
the  particles  of  liquid  and  the  metallic  surfaces  prevents  direct 
contact. 

The  kind  of  apparatus  varies  with  the  nature  and  quantity  of 
material  under  process. 

Soiling  in  Tubes.— Test-tubes,  Fig.  356,  are  very  convenient 
implements  for  delicate  solutions,  assays,  and  the  like,  and,  there- 
fore, the  laboratory  should  be  supplied  with  a  large  assortment, 
varying  from  three  inches  in  length  and  a  quarter  inch  in  dia- 
meter to  six  inches  in  length  and  one  inch  in  diameter.  They 
should  be  of  hard,  white  German  glass,  free  from  lead,  with 
perfectly  round  bottoms,  uniformly  thin,  so  as  to  withstand  heat. 
The  rack,  Fig.  39,  serves  as  their  support. 

A  test-tube  should  never  be  charged  with  more  than  one-third 
its  capacity  of  solvent,  else  there  may  be  loss  by  ejection  from 
too  sudden  ebullition;  and  the  solid  substance,  previously  pow- 


446 


SOLUTION. 


dered,  is  not  to  be  added  until  the  liquid  is  brought  to  boiling, 
and  then  only  in  small  portions  at  a  time. 

To  guard  against  spirting,  and  to  insure  a  uniform  heating,  the 
tube  must  be  gradually  heated,  not  upon  its  bottom,  but  near  to 


Fig.  357. 


or  on  the  side,  as  shown  in  Fig.  35T.  It  is,  as  seen,  heated 
over  a  small  lamp,  being  held  in  the  fingers,  -which  are  pro- 
tected from  contact  with  the  hot  glass  by  a  doubled  strip  of  thick 

Fig.  358. 


paper  wrapped  around  the  neck  of  the  tube  for  its  support.  The 
spring  holder,  Fig.  358,  consisting  of  a  wooden  handle  affixed 
to  two  flat  pieces  of  sheet-brass,  indented  at  their  ends  so  as  to 


SOLUTION   IN  TEST-TUBES.  447 

form  a  round  catch,  and  tightened  or  loosened  by  a  slide,  would 
be  much  more  convenient  for  the  purpose. 

The  mouth  of  the  tube  during  heating,  or  whilst  its  contents 
are  being  shaken,  should  always  be  held  away  from  the  operator, 
else  ejected  matter  may  endanger  his  person  or  dress. 

Faraday  gives  the  following  valuable  advice  as  to  the  use  of 
test-tubes  for  making  solutions  with  volatile  liquids,  and  under 
pressure. 

"In  consequence  of  the  small  diameter,  and  therefore  small 
sectional  area  of  tubes,  they  are  much  stronger  relatively  to 
internal  pressure  than  larger  vessels,  such  as  flasks  of  the  same 
thickness.  An  advantage  is  thus  gained  in  some  cases  of  solu- 
tion or  digestion  in  certain  fluids,  as  alcohol,  ether,  and  even 
water,  because  it  enables  the  experimenter  to  subject  the  sub- 
stances to  temperatures  as  high  as  the  boiling-points  without  loss 
of  the  fluid,  or  occasionally  to  temperatures  still  higher,  the 
ebullition  going  on  as  it  were  under  pressure.  This  is  easily  per- 
formed with  alcohol,  ether,  and  similarly  volatile  fluids,  in  tubes 
of  four,  five,  or  six  inches  in  length,  and  of  such  diameter  as  to 
be  readily  and  perfectly  closed  by  the  finger.  Suppose  a  tube 
of  this  kind,  one-third  filled  with  alcohol,  and  held  tightly  between 
the  thumb  and  second  finger  of  the  right  hand,  its  orifice  being 
closed  by  the  forefinger  of  the  same  hand,  Fig.  339.  The  fore- 
finger is  to  be  relaxed,  and  the  heat  of  a  spirit-lamp  applied  until 
the  alcohol  begins  to  boil ;  the  forefinger  is  then  to  be  reapplied 
closely,  and  it  will  be  found  that  the  flame  of  the  lamp,  applied 
at  intervals,  is  quite  sufficient  to  keep  the  temperature  up  to  the 
boiling-point.  No  alcohol  can  evaporate,  for  the  finger  has  power 
sufficient  to  retain  the  vapor  even  were  its  force  equal  to  two 
atmospheres,  and  the  tube  itself  is  also  strong  enough  to  resist 
the  same  force. 

"  This  operation  is  very  advantageous  when  valuable  and  vola- 
tile solvents  are  in  use;  it  is  therefore  worth  while  to  refer  to 
those  points  which  indicate  the  state  and  temperature  of  the 
fluid,  and  which  make  the  practice  easy.  If  the  fluid  be  one 
which,  like  alcohol,  when  at  or  above  its  boiling-point  is  at  a 
temperature  inconvenient  to  the  hand,  then,  if  all  the  common 
air  were  allowed  to  pass  out  of  the  tube  before  closing  it,  the 
whole  tube  would  become  heated  by  the  vapor  rising  from  the 


448  SOLUTION. 

hot  liquid  beneath,  and  the  fingers  would  be  injured  ;  but  by  not 
allowing  all  the  air  to  escape,  that  portion  which  is  retained  in 
the  tube  is  always  forced  to  the  top  by  the  successive  formation 
and  condensation  of  the  vapor  below,  and  interfering  with  the 
passage  of  the  hot  vapor  to  the  part  which  it  occupies,  it  pre- 
serves that  portion  of  the  tube  at  comparatively  low  and  very 
bearable  temperatures.  The  part  thus  retained  at  a  low  tempe- 
rature is  proportionate  to  the  quantity  of  air  confined  in  the  tube ; 
this  quantity  is  usually  a  proper  one  if  the  tube  be  closed  just 
after  the  alcohol  has  begun  to  boil,  and  before  the  upper  part  of 
the  tube  has  been  heated.  If  too  much  air  has  been  expelled, 
and  the  tube  is  found  to  become  hot  above,  the  application  of 
the  flame  must  be  suspended  a  moment  or  two,  the  whole  suffered 
to  cool  below  the  boiling-point,  the  tube  opened,  the  upper  part 
cooled  slightly  by  a  piece  of  moist  paper  or  a  cold  finger,  and 
then  the  forefinger  is  to  be  reapplied  to  close  it  as  before. 

"  The  state  of  the  fluid  within  is  in  part  indicated  by  the  pres- 
sure of  the  air  or  vapor  on  the  finger,  the  latter  being  urged 
away  from  the  tube  by  a  force  proportionate  to  the  degree  of  heat 
above  the  boiling-point,  and  being  drawn  inwards  when  the  heat 
is  below  that  point.  Generally,  therefore,  the  finger  alone  will 
serve  to  ascertain  whether  the  temperature  is  above  or  below  the 
point  of  ebullition ;  but  as  the  force  required  is,  after  operating 
for  some  time  at  high  pressures,  such  as  to  diminish  the  sensi- 
bility of  the  finger  to  smaller  pressures,  it  sometimes  happens 
that,  on  lowering  the  temperature,  the  period  at  which  it  attains 
that  of  ebullition  in  the  atmosphere  cannot  be  distinguished. 
This  point  is,  however,  easily  recognized  by  relieving  the  pres- 
sure of  the  finger  slightly ;  should  the  quiescent  fluid  below  then 
burst  into  ebullition,  it  is  a  proof  that  its  temperature  is  higher 
than  the  boiling-point  at  atmospheric  pressure,  but  should  it  re- 
main quiescent  until  the  finger  is  entirely  removed,  its  tempera- 
ture will  be  known  to  be  below  that  point." 

Boiling  in  Beaker  Glasses  and  Flasks. — These  vessels  are 
used  when  large  quantities  of  liquid  are  to  be  operated  upon. 
When  the  direct  heat  of  the  lamp  is  applied,  it  should  be  diffused 
by  the  intervention  of  a  wire  gauze.  The  preferable  mode  of 
heating  is  by  a  highly  heated  sand-bath.  The  same  remarks  as 
to  their  material  and  construction,  as  given  before  at  p.  271,  are 


BOILING   IN   CAPSULES. 


449 


applicable  in  this  instance.  They  should  be  loosely  covered 
during  the  operation,  the  beaker  glasses  with  capsules,  and  the 
mouths  of  the  flasks  with  watch-glasses.  The  position  of  the 
beaker  glass  over  the  lamp  is  shown  at  Fig.  347,  that  of  flasks 
at  Fig.  155.  Round-bottomed  flasks,  Figs.  359,  360,  361,  are 


Fisr.  3f>9. 


Fig.  360. 


Fig.  361, 


Fig.  362. 


made  of  different  sizes,  especially  for  solutions;  but  Florence 
flasks,  Fig.  362,  which  have  been  rounded  on  the  edges  of  the 
mouth  over  the  blowpipe  flame,  so  as  to  allow  the  easy  en- 
trance of  a  loose  cork,  are  equally  convenient  and  less  costly. 
They  are  thin  and  uniform  throughout,  and  bear  very  high  tem- 
peratures without  fracture.  Annexed  are  drawings,  also,  of  two 
wide-mouth  boiling  flasks,  which,  like  the  above,  have  round 
bottoms. 


Fig.  363. 


Fig.  364. 


Boiling  in  Capsules.— Solution  is  made  in  open  vessels  when 
the  solvent  liquid  is  not  easily  vaporizable  or  alterable  by  expo- 

X* 


450 


SOLUTION    BY   STEAM. 


sure,  or  when  its  loss  is  of  little  consequence.  The  most  conve- 
nient implements  for  the  purpose  are  porcelain  capsules,  Figs. 
365,  366.  Those  from  the  French  and  Royal  Prussian  factories 

Fig.  365.  Fig.  366. 


are  far  superior  to  those  of  any  other  make.  They  are  strong, 
yet  uniformly  thin  throughout,  and  support  very  high  tempera- 
tures and  sudden  changes.  Being  enamelled,  they  are  protected 
from  the  action  of  acids  or  corrosive  liquids,  and  consequently 
are  of  general  application.  They  are  sold  of  all  sizes,  varying 
upwards  from  an  ounce  to  18  oz.  in  capacity.  The  diameter  of 
the  smallest  is  about  two  inches,  and  that  of  the  largest  15J 
inches.  The  depth  should  be  one-third  of  the  diameter.  The 
smaller  sizes  come  in  nests  of  a  half  dozen  or  more.  Fig.  365 
represents  one  with  spreading  rim  and  lip  to  facilitate  pouring. 
That  shown  in  Fig.  366  has  a  more  hemispherical  shape. 

Capsules  are  almost  always  heated  over  the  open  fire,  the  spirit 
or  gas  lamp  furnishing  the  requisite  temperature.  Those  of 
smaller  size  are  shown  in  position  upon  suitable  supports  at  Fig. 
154,  and  z,  Fig.  155 ;  and  for  the  larger,  Luhme"s  lamp,  Fig. 
158,  answers  an  admirable  purpose. 

The  liquid  is  placed  in  the  capsule  before  the  ignition  of  the 
wick,  and  when  it  is  boiling,  the  substance  to  be  acted  on  should 
be  gradually  deposited  in  it  in  a  finely  divided  state,  during  con- 
stant stirring  with  a  glass  rod.  After  all  has  been  added,  both 
ebullition  and  stirring  must  be  continued  until  the  completion  of 
the  process,  care  being  taken  to  supply  the  loss  of  the  volatilized 
portion  by  fresh  additions  of  the  solvents,  unless  the  solution  is  to 
be  evaporated. 

When  the  nature  of  the  materials  requires  the  intervention 
of  a  medium  other  than  sand  to  modify  the  heat,  a  rare  occur- 
rence when  operating  in  capsules,  the  latter  are  heated  over 
baths,  as  shown  at  Fig.  200.  Capsules  or  boiling  pans  of  ena- 
melled ironware  or  tinned  copper  are  used  only  in  very  large 
operations. 

SOLUTION  BY  STEAM. — When  a  substance  is  to  be  dissolved 


SOLUTION   BY  STEAM.  451 

by  steam  heat,  and  the  nature  of  the  materials  renders  the  direct 
application  of  steam  inadmissible,  then  baths,  Fig.  18,  come  very 
appropriately  into  play. 

For  aqueous  solutions  which  are  greatly  facilitated  by  the 
immediate  action  of  steam,  it  is  supplied  through  flexible  lead 
tubes,  leading  from  the  generator,  Fig.  15,  directly  into  the  con- 
taining vessel. 

For  small  operations  in  glass  vessels,  the  copper  spritz,  Fig. 
240,  half  filled  with  water,  and  heated  over  the  gas  lamp,  readily 
furnishes  sufficient  steam. 

As  boiling  by  steam  is  practised  in  numerous  chemical  opera- 
tions, it  is  proper  to  introduce  some  directions  pertinent  to  the 
subject. 

It  is  very  seldom  that  the  heat  required  for  ordinary  labora- 
tory purposes  exceeds  that  given  by  five  pounds,  or  at  furthest 
fifteen  pounds,  above  atmospheric  pressure,  and  the  fire  under 
the  generator  and  weights  upon  the  safety  valve  should  be  regu- 
lated accordingly. 

If  the  mixture  to  be  boiled  is  unalterable  by  the  action  of 
condensed  steam,  the  conduit-pipe  may  lead  directly  into  it,  and 
to  the  bottom. 

As  the  liquid  appears  to  boil  before  it  actually  does,  the  only 
sure  indication  of  temperature  is  to  be  obtained  by  a  thermome- 
ter, Fig.  119. 

This  method,  however,  causes  a  great  loss  of  heat  and  incom- 
modes the  operator,  by  filling  the  apartment  with  clouds  of  vapor. 
A  loose  cover  will  partially  remove  these  objections.  In  boiling 
in  this  way,  care  must  be  taken  that  the  fire  does  not  get  low, 
lest  a  condensation  of  the  vapor  occupying  the  upper  part  of  the 
boiler  causes  a  partial  vacuum,  and  the  consequent  drawing  over 
of  part  of  the  liquid  from  the  vat  into  the  boiler.  The  conduit 
connected  with  the  feeder  should  always  have  a  stop-cock  near 
the  coupling,  which  is  to  be  shut  off  upon  the  completion  of  the 
operation.  If  the  boiler  should  then  happen  to  be  surcharged 
with  steam,  it  must  be  blown  off  through  the  valve,  this  being 
readily  accomplished  by  gradually  unloading  the  lever. 

A  far  better  plan  of  boiling  by  steam  is  to  conduct  it  through 
a  coil  of  pipe  placed  at  the  bottom  of  the  vat,  and  having  an 
exhausting-pipe  leading  into  the  neighboring  flue.  This  mode 


452 


SOLUTION   BY   DISPLACEMENT. 


Fig.  367. 


allows  a  uniform  temperature  at  any  degree,  upwards,  from 
that  of  the  atmosphere — suitable  stop-cocks  being  attached  for 
that  purpose  to  regulate  the  supply  of  steam  accordingly. 

In  cold  weather,  and  especially  when  the  feeder  or  conduit  are 
of  any  length,  it  will  be  economical  to  wrap 
them  with  woollen  listings  or  straw,  as  means 
of  preventing  condensation. 

SOLUTION  BY  DISPLACEMENT.  —  Displace- 
ment, termed  also  lixiviation,  when  applied 
to  the  solution  of  saline  substances,  is  an 
economical,  speedy,  and  efficient  means  for 
the  extraction  of  the  soluble  portions  of  woods, 
leaves,  flowers,  barks,  precipitates,  and  similar 
matters,  by  the  infiltration  of  a  liquid  solvent 
through  them.  This  process  is  equally  appli- 
cable for  maceration,  infusion,  and  decoction; 
for  though  operating  in  the  cold,  it  accom- 
plishes its  purpose. 

For  delicate  operations,  and  those  con- 
ducted upon  a  scale  of  moderate  extent,  glass 
vessels  may  be  employed.  One  of  the  usual 
form  is  shown  in  Fig.  367.  It  is  made  of  hard  glass,  free  from 
Fig.  368.  lead,  the  upper  part,  or  A,  being  the  displacer,  and 
the  lower  part,  B,  an  ordinary  flask,  the  recipient 
of  the  saturated  solution.  The  mouth  of  the  bottle 
and  that  portion  of  the  displacer  which  rests  in  it 
should  be  ground  so  as  to  make  a  close  joint. 
The  stopple  is  for  closing  the  upper  vessel  when 
necessary.  Dobereiner's  modification  of  the  above, 
but  operating  upon  the  same  principle,  is  shown  in 
Fig.  368.  To  prevent  the  passage  of  the  material 
through  the  barrel  of  the  displacer,  it  must  be  loosely 
closed  with  a  plug  of  raw  cotton  as  at  f,  and  then 
adjusted  by  means  of  a  perforated  cork  g,  with  the 
vertical  tubulure  of  the  globular  receiver  a.  The 
whole  apparatus  as  adjusted  is  retained  in  an  upright 
position  by  a  support,  the  receiver  resting  upon  a  braided  straw 
ring.  It  is  then  ready  to  receive  its  charge.  The  substance  in 
coarse  powder  and  moistened,  occupies  the  part  of  the  vessel  £, 


SOLUTION   BY   DISPLACEMENT. 


453 


Fig.  369. 


and  the  solvent  is  subsequently  added  as  at  d.  A  partial  vacuum 
being  made  in  the  receiver  by  the  evaporation  of  a  few  drops  of 
alcohol  added  through  the  lateral  stoppered  tubulure  <?,  the  liquid 
percolates  through  the  solid  mass  by  the  force  of  atmospheric 
pressure,  and  ultimately  reaches  the  receiver  saturated  with  the 
soluble  matter  of  the  material  e. 

In  order  to  express  clearly  the  rationale  of  this  process,  we 
will  suppose  that  vegetable  matter,  a  dye-wood  for  example,  in 
coarse  powder,  is  to  undergo  exhaustion  by  this  method.  It  oc- 
cupies the  part  e,  as  before  said,  and  to  facilitate  the  percolation, 
has  been  previously  moistened  with  a  portion  of  the  solvent.  If 
the  substance  swells  easily  it  must  be  packed  lightly.  Liquid  is 
added,  as  shown  at  d,  and  soon  soaks  into  the  mass  beneath ; 
another  portion  of  the  solvent  is  then 
poured  in  as  before,  and  takes  the 
same  course,  displacing  the  portion 
before  used  without  mixing  with  it. 
These  strata  of  solvent  are  pressed 
downwards  by  successive  additions  of 
liquid,  and  become  more  and  more 
charged  with  soluble  matter,  as  they 
approach  the  bottom  of  the  mass,  until 
at  last  they  run  out  into  the  recipient 
highly  charged,  and,  in  the  present  in- 
stance, highly-colored ; — the  first  run- 
nings being  more  nearly  saturated 
than  those  which  follow.  When  by 
consecutive  additions  of  solvent  the 
material  has  become  exhausted,  the 
liquid  passes  through  the  mass  and 
reaches  the  receiver  as  tasteless  and 
uncolored  as  when  first  poured  in. 
This  indicates  the  completion  of  the 
process. 

Robiquet's  displacer,  which  differs 
somewhat  from  the  preceding,  is  shown 
by  the  annexed  drawing,  Fig.  369.     It  consists  of 
ground  glass  stopper  A,  and  a  receiving  bottle  c. 

The  body,  m  n  o  p,  of  the  stopper  is  hollow,  and  pierced  with 


barrel  B,  a 


454 


SOLUTION    BY    DISPLACEMENT. 


Fip.  370. 


a  hole/,  of  about  one-tenth  of  an  inch  diameter.  There  are  cor- 
responding holes  also  in  its  bottom  e,  as  well  as  at  d  and  h  of 
the  barrel,  and  g  of  the  receiver. 

When  the  stopper  is  placed  in  the  mouth  of  the  barrel,  so  that 
the  two  holes /and  d  come  together,  there  is  still  a  communica- 
tion between  the  external  air  and  the  interior  of  the  barrel,  which 
is  further  established  by  bringing  the  two  other  openings  g  and 
h  into  coincidence. 

It  will  be  readily  seen,  therefore,  that  the  internal  pressure  of 
the  air,  and  the  flow  of  the  percolating  liquid,  can  be  regulated 
at  pleasure,  merely  by  turning  the  barrel  more  or  less,  so  as  to 
shut  or  close  the  opening  as  may  be  desired. 

The  neck  of  a  retort,  with  its  smaller  end  adjusted  to  a  wide- 
mouth  bottle  by  means  of  a  perforated  cork,  makes  an  excellent 
displacing  apparatus. 

When  the  solvent  is  volatile,  in  order  to  prevent  loss  by  eva- 
poration, the  apparatus  must  have  a  modified  form,  as  shown  in 
Fig.  370.  The  displacer  is  adapted  to  the 
centre  tubulure  of  a  two-necked  Wolfie  bottle. 
As  atmospheric  pressure  is  an  important  agent 
of  this  process,  it  will  not  do  to  shut  it  off  by 
closing  the  top  of  the  displacer  without  making 
some  compensating  arrangement,  and,  therefore, 
a  communication  between  the  upper  and  lower 
vessel  is  established  by  means  of  a  bent  tube 
adjusted  in  the  lateral  tubulure  of  each.  In 
this  manner  the  vessel  is  completely  closed,  and 
vaporization  prevented,  while  the  pressure  pro- 
duced is  distributed  throughout  the  vessel,  and 
thus  rendered  uniform.  In  using  the  glass  dis- 
placement apparatus  first  described,  this  prin- 
ciple must  be  recollected ;  where  a  vacuum  is  not  artificially 
created  in  the  receiver,  the  ground  glass  edges  of  it  and  the  dis- 
placer should  either  be  permanently  separated  or  occasionally 
disjointed. 

The  stop-cock  near  the  bottom  of  the  receiver  allows  the  with- 
drawal of  the  solution  as  fast  as  it  accumulates,  without  the 
necessity  of  disarranging  the  apparatus.  In  experiments  upon 
large  quantities  of  material,  and  in  pharmaceutical  operations 


SOLUTION   BY   DISPLACEMENT. 


455 


Fig.  371. 


generally,  the  displacers  employed  are  made  of  tinned  copper  or 
tinned  plate.  Those  of  porcelain,  which  are  now  in  the  market, 
are  much  more  serviceable,  because  they  are  readily  cleansed 
and  resist  the  action  of  corrosive  liquids.  Of  whatever  material 
they  are  made,  they  should  be  cylindrical  and  funnel-shaped  at 
the  base,  and  the  height  should  be  at  least  four  times  the  diame- 
ter, as  is  shown  in  Fig.  3T1.  At  a  there  is  a  flange  in  the  interior 
as  a  support  for  the  cullendered  dia- 
phragm a  b.  These  diaphragms  are  re- 
movable, and  for  convenience  in  handling 
have  a  knob  in  the  centre.  The  lower 
diaphragm  is  always  to  be  covered  with  a 
circle  of  coarse  muslin,  for  the  reception 
of  the  material,  and  to  prevent  the  pas- 
sage of  particles  as  well  as  obstruction  of 
the  holes.  The  other  diaphragm,  fitting 
loosely  to  the  cylinder,  rests  upon  the 
top  of  the  powder,  and  serves  for  the 
better  distribution  of  the  solvent  and  for 
the  prevention  of  the  escape  of  dusty 
particles,  which  sometimes  occurs  if  the 
powder  is  put  in  dry.  The  stop-cock  c 
in  the  barrel  or  exit-pipe  is  useful  for 
regulating  the  discharge  of  the  liquid. 

The  tripod  D  is  the  support,  and  allows 
the  withdrawal  of  the  receiver  P,  when  it  is  full,  and  when  it  is 
to  be  replaced  by  another,  without  the  necessity  of  disturbing  the 
displacer. 

Payen's  is  another  very  convenient  form  of  displacer,  in  which 
ether,  alcohol,  and  any  other  volatile  solvent  may  be  kept  in  con- 
stant action  without  exposure  to  air  or  loss  by  evaporation.  By 
its  use  a  great  saving  of  time  and  labor  and  solvent  is  gained. 
The  arrangement  is  exhibited  at  Fig.  372.  It  consists  of  a  glass 
cylinder  B,  the  funnel  of  which  should  reach  to  the  centre  of  a 
glass  balloon  A,  beneath  the  two  vessels,  being  attached  by  means 
of  a  perforated  cork.  The  lateral  tube  <?,  d,  opens  communication 
between  the  lower  and  upper  apartments.  As  the  whole  forms 
a  perfectly  tight  connection,  the  safety-tube  E  becomes  neces- 
sary for  the  regulation  of  the  dilatation  and  contraction  of  the 
vapors. 


456 


SOLUTION    BY    DISPLACEMENT. 


Fig.  372. 


When  it  is  desired  to  exhaust  a  vegetable  matter  with  alcohol 

or  ether,  and  at  one  and  the 
same  operation  to  concentrate 
the  charged  solvent,  plug  the 
barrel  of  B  with  raw  cotton,  pre- 
viously moistened  with  the  liquid 
to  be  used ;  add  the  powdered 
material,  cover  it  with  a  cullen- 
dered  disk,  pour  on  the  liquid  in 
quantity  sufficient  to  give  a  fil- 
tered solution  of  half  the  capa- 
city of  the  balloon,  and  then 
connect  the  apparatus.  The 
balloon  is  now  to  be  placed  half 
its  depth  in  the  water-bath  H, 
and  the  apparatus  sustained  in 
a  perpendicular  position  by 
means  of  a  clamp  support.  The 
water-bath  is  to  be  closed  with 
a  loose  cover,  and  heated  as  may 
be  required  by  the  small  spirit- 
lamp  I.  The  ether  or  alcohol 
which  has  infiltrated  into  the 
balloon  thus  carried  to,  and 
maintained  at  ebullition,  passes 
off  as  vapor  into  the  lateral  tube, 
there  partially  condenses  and 
falls  upon  the  material  in  the 

cylinder  to  infiltrate  through  again.  The  excess  of  vapor  and  of 
expanded  air  escapes  through  the  safety-tube ;  but  a  part  of  the 
vapor  is  arrested  and  condenses  in  the  three  bulbs,  the  first  of 
which  immediately  empties  its  liquefied  contents  into  the  cylinder 
to  renew  its  action  upon  the  powder. 

The  concentration  of  the  filtered  solution  is  thus  continually 
going  on  in  the  balloon,  the  concurrent  distillation  returning  the 
evaporated  particles  to  the  substances  to  be  exhausted,  through 
the  lateral  tube  <?,  d. 

When  water  is  the  liquid  to  be  employed,  the  water-bath  must 
be  replaced  by  a  saline  or  sand-bath,  and  the  spirit-lamp  by  a 
furnace. 


SOLUTION   IN   CLOSE    VESSELS.  457 

For  the  solution  of  difficultly  soluble  substances,  displacement 
presents  many  advantages,  and  amongst  others  it  yields  a  clear 
solution,  and  supersedes  the  necessity  of  FILTRATION,  which  is 
required  for  most  solutions  made  by  infusion,  decoction,  and 
boiling.  It  is  particularly  applicable  to  the  purpose  of  procuring 
concentrated  solutions  for  EVAPORATION  to  extracts,  as  well  as 
for  making  tinctures,  &c. 

The  solvent  may  be  acid,  alkaline,  spirituous,  ethereal,  or 
aqueous  in  its  nature,  the  principle  of  its  action  being  the  same 
in  all  cases.  When  the  liquid  is  corrosive,  however,  the  vessel 
should  not  be  metallic,  but  of  glass  or  porcelain,  and  should  be 
plugged  with  asbestos  instead  of  cotton.  It  is  immaterial  whether 
the  solvent  be  applied  cold  or  warm,  save  when  the  process  is 
resorted  to  for  the  separation  of  substances  soluble  in  cold  from 
those  which  are  only  soluble  in  hot  liquids.  Except  in  such  cases 
heat  may  be  used,  as  it  increases  the  power  of  the  solvent ;  and 
a  convenient  means  of  applying  it  is  to  encompass  the  apparatus 
with  a  metallic  jacket,  and  supply  the  intervening  chamber  thus 
formed  with  a  current  of  steam  from  the  generator,  Fig.  16. 

There  are  certain  conditions  necessary  to  the  success  of  this 
operation.  The  material  must  be  in  powder  of  medium  DIVISION  ; 
neither  too  fine  nor  too  coarse,  for  in  the  first  case  it  clogs  the 
cloth  and  holes  of  the  diaphragm,  and,  if  heavy  and  compact, 
retards  the  percolation  of  the  liquids.  On  the  other  hand,  when 
too  gross,  the  transit  of  the  solvent  is  so  rapid  that  the  material 
is  but  partially  acted  upon.  When  alcohol  or  ether  is  used,  the 
powder  may  be  a  little  finer  than  for  less  volatile  solvents ;  and 
all  powders  liable  to  set,  or  to  become  so  compact  as  to  prevent 
the  passage  of  liquid,  must  previously  be  mixed  with  well-washed 
coarse  white  sand.  This4addition  remedies  the  defect  and  insures 
the  easy  passage  of  the  solvent. 

The  material,  as  before  recommended,  should  be  moistened 
with  half  its  weight  of  the  solvent,  and  left  to  soak  for  an  hour 
or  more  before  being  placed  in  the  percolator.  After  having 
been  transferred,  it  is  covered  with  the  diaphragm,  and  sufficient 
liquid  is  poured  upon  it  to  cover  entirely  its  surface.  As  soon  as 
this  first  portion  infiltrates  through  the  mass,  another  portion  is 
added ;  for  it  is  only  by  keeping  the  surface  covered  with  solvent 
that  a  uniform  penetration  of  all  portions  of  the  mass  can  be 


458 


CADET  S   MODE    OF   SOLUTION. 


effected.  If  the  liquid  passes  through  very  rapidly,  the  mass  is 
too  loose,  and  must  therefore  be  compressed  by  pressing  upon 
the  diaphragm  cover.  Or,  in  order  to  prolong  their  contact,  the 
stop-cock  c  may  be  nearly  closed,  so  as  to  allow  the  exit  of  only 
a  thin  stream. 

When  alcohol  or  other  valuable  volatile  liquid  is  used,  the  resi- 
dual portions  may  be  either  extracted  by  pressure  of  the  mass  P, 
or  by  displacement  with  water ;  and  subsequently,  by  distillation 
of  the  resulting  mixture.  The  general  practice,  however,  in  the 
laboratory  is  to  reserve  the  last  running  for  the  first  application 
to  fresh  material. 

CADET'S  MODE  OF  SOLUTION. — This  plan  is  well  adapted  to 
those  powders  which  do  not  admit  of  being  easily  infiltrated. 
It  consists  in  macerating  or  infusing  the  pulverized  material 
with  double  its  weight  of  cold  or  hot  solvent,  and  after  some 
time  subjecting  it  to  strong  pressure.  This  treatment  is  to  be 
repeated  until  the  substance  ceases  to  yield  soluble  matter,  and 
the  resulting  liquids  are  then  mixed  together  and  filtered. 
Cadet's  mode  is  used  largely  for  dissolving  the  tannin  from  galls 
with  ether. 

A  suitable  press  for  this  purpose  is  shown  at  Figs.  373  and 
374.  All  powders  which  have  undergone  the  process  of  solution 


Fig.  373. 


Fig.  374. 


n 


in  large  quantity  should  be  subjected  to  its  action,  as  a  good 
deal  of  retained  solution  may  thus  be  obtained,  and  consequently 
saved. 

It  is  formed  of  two  strong  upright  stanchions,  and  two  propor- 
tionably  strong  cross-pieces,  firmly  jointed  in  the  side-beams. 
T.ie  upper  cross-piece  carries  a  box  through  which  works  an  ordi- 


CADET'S  MODE  OF  SOLUTION.  459 

nary  press  screw,  in  the  usual  manner.  Upon  the  lower  cross- 
piece,  is  placed  a  wooden  trough,  A  (Fig.  374),  at  least  two 
inches  deep,  and  to  the  front  of  which  is  adapted  a  gutter  B,  for 
the  conveyance  of  the  liquid,  which  assembles  in  the  trough,  to 
a  vessel  E,  placed  at  and  beneath  its  mouth.  Upon  and  within 
the  trough  is  placed  a  wrought-iron  plate  cylinder.  This  cylin- 
der is  formed  of  two  semi-cylinders  joined  together.  Throughout 
its  height,  it  is  divided  off  alternately  into  equal  parts  by  zones 
or  belts.  The  zones  a  a  are  more  than  an  inch  broad;  the 
partition  6,  &c.,  four  or  five  inches  in  width.  The  top  as  well  as 
the  lower  zone  is  narrow.  All  the  wider  divisions  are  cullendered 
throughout  their  circumference  with  innumerable  small  holes, 
through  which  the  liquid  is  to  flow  when  pressure  is  applied. 
All  the  narrow  zones  are  secured  by  a  strong  wrought-iron  ring, 
formed  of  two  pieces  working  on  a  hinge  adjusted  at  the  back. 
Upon  the  front  is  a  movable  broach  D,  which  bolts  them  together, 
and  makes  the  cylinder  compact,  so  that  it  can  resist  the  pres- 
sure applied.  When  the  marc  is  exhausted,  by  draining  out  the 
broach  D,  the  circumference  of  the  cylinder  is  loosened  or  ex- 
tended, so  that  its  contents  can  be  removed  without  difficulty, 
The  marc  is  placed  in  this  cylinder  and  pressed  out  by  the  power 
of  the  screw,  until  no  more  fluid  will  exude,  even  with  the  force 
of  a  man  to  the  lever.  The  liquid  runs  into  the  gutter  B  and 
through  a  sieve,  which  should  be  properly  placed  for  the  purpose, 
into  the  vessel  E,  and  may  thence  be  drawn  off  after  it  has 
settled,  into  suitable  vessels.  The  residual  exhausted  powder  is, 
as  said  above,  easily  emptied  out  by  loosening  and  removing  the 
pin  D. 

A  much  more  convenient  implement  than  the  preceding  is  the 
lever  press,  described  in  Muspratt's  Chemistry,  and  a  perspective 
view  of  which  is  shown  by  Fig.  375.  It  consists  of  two  wrought- 
iron  pillars  B  B,  supported  in  sockets  by  the  cast-iron  feet  A  A. 
The  bed-piece  c  is  also  secured  to  the  feet  by  two  perforated  ears, 
and  has  two  intersecting  grooves  sunk  into  its  surface,  as  chan- 
nels for  conducting  off  the  expressed  liquid.  The  follower  D, 
corresponding  in  size  with  the  bed-piece  c,  is  adjusted  to  the  pillars 
by  sliding-ears,  and  has  the  rack-bar  F  fixed  in  the  centre.  The 
gearing  is  sustained  by  framework  E  attached  to  B  B.  Motion 
is  effected  as  follows:— The  ratchet-wheel  G  turns  upon  an  axle 


460 


CADET  S    MODE   OF    SOLUTION. 


having  its  bearings  in  the  top  frame.     On  the  same  centre  is  a 
fixed  pinion  of  eight  teeth,  only  partially  seen  in  the  figure,  which 

Fig.  375. 


Fig.  376. 


works  in  the  wheel  I,  of  twenty-four  cogs ;  and  upon  the  axis  of  I 
is  another  eight-teeth  pinion,  which  acts  upon 
the  rack.  The  lever  K  is  forked  at  the  extre- 
mity nearest  the  small  winch-handle  L,  and  the 
terminations  of  the  furcation  are  received  upon 
the  axle  G.  A  pin,  near  H,  is  adapted  to  a  small 
9  hole  in  the  frame,  by  the  insertion  of  which  the 
'  descent  of  the  lever  may  be  prevented.  The 
matter  to  be  pressed  is  placed  in  a  shallow, 
cylindrical  box  A,  of  tinned  copper,  Fig.  376, 
which  rests  upon  the  bed  c  of  the  press.  To 
prevent  the  contents  from  being  pressed  against 
the  sides  of  the  cylinder,  and  thus  obstructing  the  flow  of  the 
liquid  thence,  it  is  necessary  to  use  a  perforated  band  with  per- 
pendicular ribs  on  the  exterior.  Being  movable  and  formed  of 
two  parts  joined  together  by  a  hinge,  it  can  be  easily  put  in 
proper  position  around  the  matters  to  be  pressed  (after  the  latter 
has  been  placed  in  the  box),  and  fastened  by  means  of  the  pin. 
The  ribs  on  the  outer  circumference  of  this  band  project  against 


SOLUTION  UNDER   PRESSURE  OP  STEAM.  461 

the  inner  sides  of  the  box,  and  form  intermediate  grooves,  through 
which  the  expressed  liquid,  issuing  from  the  holes,  can  readily 
pass  off  into  the  receiving  vessel  at  the  spout  beneath. 

To  put  the  press  in  action,  the  lever  being  upheld  by  the  pin 
at  H,  the  winch-handle  is  turned  to  the  left,  in  order  to  lower  the 
rack  and  follower,  until  the  latter  presses  upon  the  wooden  block 
B,  Fig.  376,  which  caps  the  material  under  pressure.  The  lever 
is  then  raised,  and  the  pall  allowed  to  work  into  the  ratchet, 
which  will  cause  the  latter  to  turn,  and  produce  the  descent  of 
the  rack.  This  is  repeated,  if  requisite,  until  a  considerable 
pressure  is  obtained ;  and  should  it  be  desired  to  go  on,  the  lever 
is  elevated  considerably  above  the  horizontal  line,  and  left  to 
follow  the  consolidation  of  the  contents  of  the  bag.  If,  however, 
this  is  unnecessary,  the  pin  H  is  inserted,  upon  which  the  lever 
remains.  The  amount  of  pressure  is  also  regulated  by  the  dis- 
posal of  the  weight  M  in  the  various  notches  of  the  lever. 

When  it  is  not  expedient,  as  in  the  case  of  pulpy  and  similar 
matters,  to  press  the  substance  in  the  box  without  first  enveloping 
it  in  a  cloth,  it  may  be  wrapped  in  unbleached  Russia  canvas ; 
and  the  bag-shape  bundles  thus  formed  placed  in  the  box,  with  a 
stiff  plate  of  tinned  copper  interposing  every  two  of  them.  They 
should  be  folded  so  as  not  to  make  a  thickness  of  more  than  an 
inch. 

As  the  cloths  absorb  a  considerable  quantity  of  the  expressed 
juice,  and  occasion  loss,  the  pressing  should  be  accomplished 
without  them  in  all  possible  cases.  The  cloths,  used  for  confining 
substances  from  which  oily  liquid  is  to  be  expressed,  must  be 
woollen  and  thick. 

The  pressure  must  be  in  all  cases  gradual  at  the  commencement. 

Solution  under  Pressure  of  Steam.— Figs.  377  and  378  ex- 
hibit Duvoir's  bucking  apparatus,  which,  as  modified  in  the  draw- 
ings, is  applicable  to  the  exhaustion  of  organic  matter.  B  B  are 
the  wooden  vats  lined  with  lead  which  receive  the  material  to  be 
displaced ;  G  G  the  cullendered  diaphragms  for  its  support ;  and 
c  c  their  movable  covers  counterpoised  so  as  to  admit  of  ready 
depression  or  elevation  at  will.  These  false  bottoms  are  also 
movable,  so  as  to  afford  facility  in  cleansing  the  vat,  and  they 
should,  when  in  use,  be  covered  with  crash  cloths  to  prevent  ob- 
struction of  the  holes.  The  tubes  D  D,  communicating  with  the 


462 


SOLUTION    UNDER   PRESSURE    OF    STEAM. 


steam  generator,  Fig.  16,  traverse  the  centre  of  the  vats,  and  are 
surmounted  by  metallic  disks,  E  E,  for  the  reverberation  of  the 
vapor  rushing  against  them. 


Fig.  377. 


Fig.  378. 


The  directions  for  the  management  of  the  apparatus  are  nearly 
the  same  as  for  displacement  generally.  When  the  vat  has 
received  its  charge,  the  cover  is  to  be  lowered  and  fastened  down 
by  clamps,  and  steam  let  on  by  opening  the  stop-cock  of  the 
feeder.  As  the  steam  generates,  it  passes  over  through  the  pipe 
r>,  reaches  the  disk  E,  and  is  projected  uniformly  over  the  whole 
surface  of  the  material.  The  elastic  force  of  the  vapor  accumu- 
lating in  the  upper  portion  of  the  vat  exerts  a  pressure  upon  that 
portion  which  has  condensed,  and  forces  it  downwards  through 
the  mass.  In  its  passage  it  becomes  charged  with  soluble  matter 
and  reaches  the  lower  part  of  the  vat  K  beneath  the  diaphragm, 
whence  it  is  drawn  off  through  the  cock  L,  R. 

As  a  protection  against  accidents,  there  should  be  a  safety- 
valve  upon  the  cover  of  the  vat  as  well  as  upon  the  generator. 

This  arrangement  would  be  particularly  economical  in  the  arts, 
for  extracting  dyewoods  and  other  vegetable  substances. 


EVAPORATION. — EVAPORATING   VESSELS.  463 

CHAPTER  XXII. 

EVAPORATION. 

WHEN  any  liquid  is  heated  for  the  purpose  of  expelling  vapo- 
rizable  matter,  and  the  process  is  conducted  solely  with  a  view 
to  saving  its  fixed  portion,  the  operation  is  termed  evaporation. 
It  thus  far  differs  from  distillation,  which  has  for  its  object  the 
preservation  of  the  volatilized  portion,  in  most  cases,  regardless 
of  the  solid.  By  its  aid  we  can  decrease  the  volume  of,  or  con- 
centrate solutions  for  crystallization  and  chemical  reaction,  expel 
valueless  volatile  ingredients  from  those  which  are  more  fixed, 
obtain  dissolved  matter  in  a  dry  statej-  and  prepare  extracts  and 
other  pharmaceutical  products. 

Liquids  evaporate  more  or  less  at  all  temperatures,  those  having 
the  lowest  boiling-point  yielding  the  most  readily ;  but  there  are 
certain  conditions  which  greatly  promote  this  tendency.  It  must 
be  remembered,  therefore  : — 

1.  That  evaporation  is  more  rapid  in  dry  atmospheres,  and 
that  consequently  the  transit  of  a  constant  stream  of  air  over  the 
surface  of  the  heated  liquid  effects  a  continual  removal  of  each 
stratum  as  it  becomes  saturated  with  vapor. 

2.  That  evaporation  is  confined  to  the  surface,  and  conse- 
quently that   the   breadth  of  the   evaporating  vessel  must  be 
extended  at  the  expense  of  its  depth. 

3.  That  heat  greatly  facilitates  evaporation  by  lessening  the 
cohesive  force  of  the  particles  of  a  liquid,  and  consequently  that 
the  evaporating  vessel  should  present  a  broad  heating  surface. 

4.  That  a  diminution  of  the  atmospheric  pressure  also  facili- 
tates evaporation,  for  the  more  perfect  the  vacuum  the  lower  the 
boiling-point  of  a  liquid. 

Evaporating  Vessels.— For  analytic  purposes,  capsules  are  by 
far  the  best  implements.  The  capsules  should  be  very  thin, 
nearly  flat-bottomed,  with  steep  sides,  a  spout  for  pouring,  and 
glazed  throughout.  Watch-glasses  answer  for  small  experiments, 
but  require  to  be  very  cautiously  heated,  as  they  are  readily 
fractured. 

Beaker  glasses  are  also  used  for  evaporating  solutions  which 


464 


SPONTANEOUS  EVAPORATION. 


would  lose  by  being  transferred.  Broad-niouthed  glass  flasks 
are  only  employed  for  slow  processes  with  valuable  liquids,  which 
are  liable  to  alteration  by  too  much  exposure  when  ebullition  is 
necessaty.  They  must  be  made  uniformly  thin  throughout,  of 
hard  German  glass,  free  from  lead,  and  with  flat-bottoms,  to  give 
them  a  broad  heating  surface  and  a  steady  position  in  the  baths, 
in  which  they  are  generally  placed  to  be  heated.  Figs.  379  and 
380  present  the  usual  forms  of  matrass  for  evaporations. 


Fig.  379. 


Fig.  380. 


Fig.  381. 


For  the  larger  operations  of  the  chemist  or  pharmaceutist, 
vessels  (Fig.  381)  of  copper,  tin,  ena- 
melled iron,  tinned  copper,  and  for  some 
purposes  very  large  porcelain  capsules, 
are  more  suitable. 

Retorts  are  used  when  the  vaporized 
particles  are  of  sufficient  value  to  be 
condensed,  as  in  the  process  of  distilla- 
tion. 

Spontaneous  Evaporation. — Those  liquids  which  are  very  vola- 
tile, or  which  become  altered  by  heat,  are  evaporated  by  mere 
exposure  to  the  atmosphere  at  its  ordinary  temperature.  To  this 
end  they  are  poured  into  broad  shallow  vessels,  and  placed  aside 
until  the  dissipation  of  all  vaporizable  matters,  or  until  crystal- 
lization ;  this  mode  of  evaporation  being  also  employed  for  pro- 
curing large  crystals,  which  are  better  defined  than  those  obtained 
by  rapid  evaporation. 

The  more  dry  and  hot  the  atmosphere  the  more  rapid  is  the 


EVAPORATION   IN   VACUO.  465 

evaporation,  because  its  capacity  for  dissolving  moist  vapors  is 
much  greater  at  high  than  low  temperatures.  In  order  to  main- 
tain a  continued  contact  of  the  surface  of  the  liquid  with  strata 
of  fresh  air,  the  vessel  containing  it  should  be  placed  in  a  draught, 
so  that  those  portions  of  air  which  become  saFurated  with  vapor 
may  be  displaced.  The  air-chamber  of  the  jack  furnishes  an 
efficient  means  of  spontaneous  evaporation. 

When  the  air  might  act  injuriously,  and  a  vacuum  is  unneces- 
sary, a  substance  may  be  evaporated  in  another  atmosphere,  for 
instance,  of  hydrogen  or  carbonic  acid.  For  this  purpose,  it  is 
only  necessary  to  adjust  the  disengagement-leg  of  the  apparatus 
(Fig.  172)  to  the  tubulure  of  a  retort,  so  that  its  end  may  reach 
nearly  to  the  level  of  the  liquid  in  the  latter.  The  generated 
hydrogen  passes  into  the  retort  heated  to  the  required  tempera- 
ture, and  promotes  the  discharge  of  the  vapors  into  the  recipient 
attached  to  the  beak  of  the  retort,  and  fitted  with  a  small  tube 
in  its  other  tubulure  for  the  disengagement  of  its  uncondensed 
portions. 

For  the  evaporation  of  solutions  of  sulpho-bases,  of  sulpho- 
salts,  and  of  all  substances  readily  oxidizable  by  exposure,  this 
process  is  better  applicable  than  that  with  the  air-pump,  which 
is  apt  to  be  attacked  when  the  eliminated  vapors  are  corrosive. 

This  process  is  much  used  in  CRYSTALLIZATION,  for  concentra- 
ting alterable  solutions,  and  drying  precipitates. 

Evaporation  in  Vacuo. — We  have  already  referred  to  the 
happy  influence  of  diminished  atmospheric  pressure  in  facilita- 
ting evaporation,  and  shall  now  speak  of  the  means  by  which 
it  is  accomplished,  and  the  particular  instances  in  which  it  is 
employed. 

This  mode  is  resorted  to  for  hastening  the  evaporation  of  all 
liquids  at  low  temperatures,  but  more  especially  of  those  which 
would  be  alterable  by  exposure  to  air  during  the  process. 

In  small  experiments,  a  capped  bell  glass  H,  Fig.  47,  is  used 
as  the  confining  space.  Under  this  bell  is  placed  the  broad, 
shallow  capsule,  with  its  liquid  contents,  supported  upon  a 
wire  tripod,  resting  in  a  leaden  tray  containing  sulphuric  acid, 
dried  chloride  of  calcium,  fused  potassa,  or  some  other  absorbent 
material  (DESICCATION).  The  bottom  or  bed  of  the  bell  may  be 
a  ground  glass  plate,  and  to  seal  the  joints  hermetically  the  rim 

30 


466  EVAPORATION   IN   VACUO. 

of  the  bell  should  be  greased.  Connection  being  made  by  means 
of  a  suitable  pipe,  and  the  stop-cocks  between  the  bell  and  the 
syringe,  communication  is  opened  and  the  vessel  exhausted  of  air. 
The  pressure  being  thus  removed,  evaporation  proceeds  rapidly ; 
and  until  the  absorbent  matter  becomes  saturated  with  vaporized 
particles,  or  the  bell  filled,  there  is  no  impediment.  The  latter 
can  be  partially  removed  by  working  the  pump  at  frequent  in- 
tervals. 

When  an  air-pump  is  used,  the  procedure  is  the  same ;  but,  in 
either  case,  the  vacuum  must  be  produced  gradually,  otherwise 
the  sudden  ebullition  of  the  liquid  may  cause  ejection  of  its  par- 
ticles. The  better  way  is  to  cease  pumping  as  soon  as  the  baro- 
meter attached  to  the  machine  indicates  from  two  to  two  and  a 
half  inches  pressure,  and  to  resume  the  process  of  exhausting 
again  at  intervals  of  fifteen  or  thirty  minutes. 

Other  modes  of  evaporating  in  vacuo,  as  practised  in  the  arts, 
are  fully  described  in  lire's  Dictionary  of  Arts,  and  under  Sugar  in 
the  "Encyclopaedia  of  Chemistry"  and  "  Knapp's  Technology" 
Howard's  and  Barry's  vacuum  pans  are  the  most  effective  imple- 
ments. The  latter,  a  costly  instrument,  is  applicable  in  Phar- 
macy for  making  extracts  upon  an  extensive  scale.  It  consists 
of  a  hemispherical  pan  with  a  tightly  fitting  cover,  in  the  centre 
of  which  is  a  bent  tube  leading  into  a  copper  spheroid  of  four 
times  the  capacity  of  the  pan.  This  tube  is  fitted  with  a  stop- 
cock, which  allows  a  communication,  at  will,  between  the  spheroid 
and  pan.  Another  cock,  at  the  opposite  end,  is  made  so  as  to 
couple  with  the  conduit  of  the  steam  generator. 

The  liquid  to  be  evaporated  is  introduced  into  the  basin,  which 
is  then  to  be  hermetically  closed  and  placed  in  a  water-bath. 
The  cock  connecting  with  the  spheroid  being  closed,  a  current  of 
steam  is  let  on,  and  continued  until  the  entire  expulsion  of  air 
from  the  pan ;  access  of  steam  is  then  stopped  by  closing  the 
cocks,  and  a  sheet  of  cold  water  applied  to  the  exterior.  A  con- 
densation of  vapor  ensues,  and  a  partial  vacuum  is  produced. 
Communication  being  then  opened  with  the  caldron,  uniform  ex- 
pansion of  the  air  ensues ;  and  as  the  capacity  of  the  spheroid  is 
four  times  greater  than  that  of  the  pan,  the  latter  contains  only 
one-fifth  of  its  original  amount  of  air.  Several  repetitions  of  this 
manipulation  produce  a  sufficient  vacuum.  The  water-bath  is 


EVAPORATION  BY  HEAT  IN  OPEN  AIR.        467 

then  heated  until  the  liquid  within  the  pan  commences  to  boil,  as 
may  be  seen  through  the  small  window  left  for  the  purpose,  and 
the  cooling  of  the  spheroid  continued.  When  the  liquid  has 
reached  the  required  thickness,  the  operation  may  be  discon- 
tinued. In  this  way  ebullition  proceeds  at  100°  F.,  under  a 
pressure  sixteen  times  less  than  that  of  air.  With  an  air-syringe 
attached,  for  removing  the  vapor  as  fast  as  formed,  the  power  of 
the  apparatus  would  be  greatly  increased. 

Evaporation  ~by  Heat  in  Open  Air. — Having  already  noted 
the  effects  of  heat  in  facilitating  evaporation,  we  proceed  to  make 
known  its  modes  of  application.  As  the  boiling-points  of  solu- 
tions differ,  so  accordingly  their  evaporations  are  effected  at 
varying  temperatures.  For  example,  aqueous  or  other  solutions 
of  unalterable  matter  may  be  evaporated  over  the  fire ;  others, 
which  are  destructible  by  heat,  require  the  intervention  of  BATHS. 
In  whatever  mode  the  operation  is  performed,  the  general  prin- 
ciples are  the  same,  and  whether  the  vessel  be  a  porcelain  capsule 
or  metallic  pan,  the  greater  its  width  in  proportion  to  its  depth 
the  more  rapid  is  the  evaporation.  Constant  agitation  with  a 
stirrer  is  also  promotive  of  the  process. 

Evaporation  over  Water  and  Saline  Baths. — When  solutions 
are  alterable  at  a  temperature  above  212°  F.,  the  capsule  or 
containing  vessel  is  heated  over  the  WATER-BATH,  Fig.  150. 

If  it  requires  a  higher  heat,  but  one  not  exceeding  300°  F., 
then  the  water  must  be  replaced  by  a  SALINE-BATH,  p.  269. 

Evaporation  by  Steam. — This  mode  has  many  advantages  over 
all  others,  not  among  the  least  of  which  is  that  with  the  aid  of 
the  generator  or  jack,  Figs.  15  and  17,  any  number  of  vessels 
may  be  heated  simultaneously,  and  in  any  part  of  the  laboratory, 
it  being  only  necessary  to  have  conduits  of  sufficient  length  to 
convey  the  steam  to  them,  as  exemplified  by  the  steam  series, 
Fig.  18.  Moreover,  convenient  stop-cocks  allow  a  regulation  of 
the  heat,  and  consequently  all  danger  of  injury  to  the  evapora- 
ting solution  is  avoided.  By  increasing  the  pressure  of  the  steam 
the  temperature  of  the  solution  is  also  elevated. 

Steam  is  applied  through  metallic  coils  placed  at  the  bottom 
of  the  containing  vessels,  and  having  an  exit-pipe  leading  into 
the  neighboring  flue,  or  else  by  means  of  metallic  casings.  This 
latter  mode,  by  far  the  best,  has  already  been  described  in  detail. 


468  EVAPORATION    BY    HEATED    AIR. 

Evaporation  over  Sand-baths. — This  mode  is  much  used  in 
analyses  and  for  careful  evaporations,  requiring  temperatures 
greater  than  212°,  and  yet  not  so  high  as  those  given  by  the 
naked  fire.  The  position  and  arrangement  of  the  vessels  are  as 
directed  under  the  head  of  SAND-BATHS. 

Evaporation  by  Heated  Air. — This  mode  is  admirably  adapted 
for  the  inspissation  of  the  natural  juices  of  plants  or  for  pre- 
paring dry  extracts.  It  is  also  applicable  to  the  completion  of 
evaporations  which  have  been  carried  as  far  as  is  safe  over  the 
naked  fire.  Porcelain  plates  or  panes  of  window-glass  are  the 
vessels  used,  and  a  stove  or  apartment  for  their  reception,  heated 
from  95°  to  110°,  with  a  free  draught  passing  through,  are  the 
means  of  obtaining  the  required  temperature.  The  juice  evapo- 
rates either  to  thin  scales  or  else  to  a  spongy  mass,  as  in  the  case 
of  tannin  extracted  by  ether,  and  as  soon  as  it  reaches  dryness, 
the  plates  or  panes  are  to  be  withdrawn,  and  their  contents 
removed  with  a  spatula. 

Marcet,  of  Geneva,  who  experimented  with  water  and  alcohol, 
gives  the  following  interesting  results  of  an  investigation  into 
the  circumstances  which  promote  or  prevent  the  evaporation  of 
liquids. 

1.  The  temperature  of  a  liquid  allowed  to  evaporate  freely  in 
an  open  vessel  is  always  inferior  to  that  of  the  surrounding  atmo- 
sphere.    The  higher  the  temperature   of  the  atmosphere,   the 
greater  is  the  difference  between  its  temperature  and  that  of  the 
liquid  exposed  to  evaporation.    Between  40°  and  50°  Centigrade, 
the  difference  was  found  to  vary  from  5°  to  7°;  between  20°  and 
25°  it  varied  from  1J°  to  1J°;  at  12°  it  was  0-8°  only,  and  be- 
tween 3°  and  zero  about  0-2°.     The  explanation  of  this  result  is 
obvious.     The  evaporation. of  a  liquid  diminishing  with  the  exter- 
nal temperature,  the   cold,  which   is   the   consequence  of  this 
evaporation,  must  diminish  in  the  same  proportion ;  and  if  it  were 
possible  to  prevent  evaporation  altogether,  the  author  presumes 
that  there  would  be  no  difference  whatever  between  the  tempera- 
ture of  a  liquid  and  that  of  the  surrounding  medium. 

2.  The  temperature  of  liquids,  such  as  water  and  alcohol,  as 
well  as  the  rapidity  with  which  they  evaporate,  varies,  all  other 
circumstances  remaining  the  same,  according  to  the  nature  of  the 
vessel  in  which  these  liquids  are  contained.     For  instance,  the 


EVAPORATION   BY  HEATED   AIR.  469 

temperature  of  the  surrounding  atmosphere  being  from  15°  to 
20°,  water  is,  on  the  average,  0-3°  warmer  in  an  open  metallic 
vessel  than  in  a  similar  one  of  polished  porcelain,  and  0-2°  warmer 
than  in  a  similar  one  of  glass.  It  is  the  same  with  alcohol. 
Again,  both  water  and  alcohol  evaporate  more  rapidly  from  a 
porcelain  vessel  than  from  a  metallic  or  glass  vessel  of  precisely 
the  same  size.  For  example,  three  similar  vessels,  one  of  metal, 
the  second  of  porcelain,  and  the  third  of  glass,  containing  each 
600  grains  of  water,  having  taen  exposed  to  evaporation  during 
seven  days,  the  temperature  of  the  surrounding  atmosphere  vary- 
ing from  20°  to  25°,  it  was  found  that,  at  the  end  of  that  time, 
the  porcelain  vessel  had  lost  303  grains  of  its  previous  weight, 
the  metallic  one  277,  and  the  glass  vessel  275-5  grains  only. 
The  author  enters  into  considerable  detail  as  to  the  precautions 
he  took  to  make  sure  that  these  differences  could  not  be  attributed 
to  any  difference  in  the  radiating  or  conducting  powers  of  the 
vessels  employed.  The  differences  observed  in  the  temperature 
of  liquids,  according  to  the  nature  of  the  vessels  in  which  they 
are  contained,  depends,  no  doubt,  on  the  property  with  which 
these  vessels  appear  to  be  endowed  of  accelerating  or  delaying 
evaporation.  It  is  evident  that,  in  each  case,  the  quantity  of 
sensible  heat  subtracted  from  the  liquid,  or,  in  other  words,  the 
diminution  of  its  temperature,  must  be  in  proportion  to  the  quan- 
tity of  vapor  formed.  For  instance,  the  fact  that  water  and 
alcohol  are  constantly  colder  in  a  porcelain  vessel  than  in  a 
similar  vessel  of  metal  or  glass,  is  the  natural  result  of  the  more 
rapid  evaporation  of  these  liquids  from  the  former  of  these  ves- 
sels than  from  the  two  latter.  The  reason  why  a  porcelain  vessel 
evaporates  more  freely  than  a  metallic  or  glass  one  is  far  less 
evident.  The  author  has  proved,  by  placing  an  hermetically  closed 
bottle  of  porcelain,  containing  water,  under  the  vacuum  of  the  air- 
pump,  that  it  cannot  be  owing  to  any  perviousness  of  the  sides  of 
the  vessel,  as  he  was  at  first  inclined  to  suspect. 

3.  The  influence  of  the  mass  or  depth  of  a  liquid  was  next  exa- 
mined. The  author's  experiments  appear  to  lead  to  the  curious 
fact,  that  the  rapidity  with  which  any  given  liquor  evaporates 
depends  not  only  on  the  extent  of  its  surface,  but  also,  within 
certain  limits,  on  its  depth.  He  found,  for  instance,  that  with 
two  similar  cylindrical  porcelain  vessels  containing,  the  first  a 


470  EVAPORATION    BY    HEATED    AIR. 

layer  of  water  of  one-twelfth  of  an  inch  in  depth,  and  the  second 
a  layer  of  half  an  inch,  the  evaporation  from  the  latter  exceeded 
that  of  the  former  in  the  proportion  of  nearly  4  to  3.  A  similar 
result  was  obtained  with  alcohol.  If  thin  glass  vessels  were  used, 
the  same  increase  of  depth  accelerated  the  evaporation  in  the 
proportion  of  6  to  5.  As  the  author  himself  observes,  this  appa- 
rent influence  of  the  depth  of  a  liquid  on  its  evaporation  may, 
very  possibly,  be  merely  owing  to  the  greater  facility  with  which 
the  different  layers  are  conveyed,  the  one  after  the  other,  to  the 
surface,  when  the  liquid  is  of  a  certain  depth  than  when  it  is  quite 
shallow. 

4.  Water  containing  a  solution  of  salt  in  about  the  same  pro- 
portion of  sea-water,  evaporates  less  rapidly,  and,  consequently, 
produces  less  cold  than  the  same  quantity  of  distilled  water.    The 
higher  the  temperature  of  the  surrounding  atmosphere,  the  greater 
the  difference  between  the  quantities  of  salt  and  fresh  water  eva- 
porated in  a  given  time,  under  similar  circumstances. 

5.  A  given  quantity  of  water,  mixed  with  certain  pulverulent 
substances,  such  as  a  siliceous  sand,  for  the  particles  of  which  it 
has  but  a  slight  adhesion,  evaporates  more  rapidly  than  the  same 
quantity  of  distilled  water  alone.     The  fact  was  ascertained  in 
the  following  manner : — The  author  having  procured  two  small 
porcelain  vessels  exactly  of  the  same  size,  introduced  into  one  of 
them  300  grains  of  distilled  water,  and  into  the  other  a  small 
quantity  of  siliceous  sand,  over  which  300  grains  of  water  were 
poured,  so  as  not  only  to  saturate  the  sand,  but  also  to  leave  a 
layer  of  water  of  about  one-tenth  of  an  inch  in  thickness  over 
and  above  its  surface.     At  the  end  of  five  days,  it  was  observed 
that  the  water  standing  alone  had  lost  184  grains  of  its  previous 
weight,  while  the  water  mixed  with  the  sand  had  lost  no  less  than 
196  grains.     The  average  difference,  resulting  from  a  series  of 
experiments,  was  7J  per  cent,  in  favor  of  the  more  rapid  evapo- 
ration of  water  mixed  with  sand  compared  with  that  of  water 
standing  alone.     If  the  experiment  be  made  with  glass  or  metal- 
lic vessels,  the  difference  is  only  about  4J  per  cent. 

6.  The  last  result  which  we  shall  mention,  and  which  may  be 
regarded  as  a  direct  consequence  of  the  preceding  one,  is  the 
following:  —  Water  mixed  with  sand  remains  habitually  at  a 
slightly  lower  temperature  than  an  equal  surface  of  water  stand- 


EVAPORATION   OVER   THE   NAKED    FIRE.  471 

ing  alone.  The  difference  varies  to  a  certain  extent  according  to 
the  nature  of  the  vessels  in  which  the  experiment  is  performed, 
never,  however,  exceeding  half  a  degree  Centigrade.  It  is  greater 
when  the  comparison  is  made  between  water  and  wet  sand  placed 
in  two  similar  metallic  vessels,  than  when  they  are  placed  in  por- 
celain or  glass  vessels ;  in  the  latter  case  it  seldom  exceeds  0-1° 
to  Q'2°.—Bibliotheque  Universelle,  1853. 

Evaporation  over  the  Naked  Fire. — The  tendency  of  many 
substances  to  decomposition  over  fire,  especially  organic,  even 
when  in  solution,  renders  this  mode  inapplicable  save  when  the 
solvent  and  substance  dissolved  are  both  unalterable  below  the 
boiling-point  of  the  former.  It  is  resorted  to  for  expediting  eva- 
porations, but  otherwise  is  far  more  inconvenient  than  steam, 
because  of  its  affording  less  facility  for  the  regulation  of  the  heat 
and  requiring  greater  attention.  The  containing  vessel  should 
be  placed  over  a  furnace  of  small  dimensions,  and  its  contents 
continually  stirred  with  a  porcelain  spatula; — this  precaution 
preventing  decomposition  or  carbonization,  provided  the  tempe- 
rature is  not  allowed  to  exceed  the  boiling-point  of  the  solvent. 

In  analysis  and  other  processes,  the  heating  implement  is 
generally  the  gas  or  spirit-lamp,  Figs.  40,  41.  The  capsule  filled 
to  about  two-thirds  its  depth  with  liquid,  being  placed  in  position, 
the  flame  is  applied  gradually  and  maintained  just  low  enough  to 
prevent  ebullition ;  and  in  order  to  facilitate  the  process,  and  at 
the  same  time  to  allay  turbulence,  it  should  be  frequently  stirred 
with  a  glass  rod.  The  same  directions  apply  when  the  operation 
is  performed  in  a  beaker  glass,  as  is  done  in  some  analytic  expe- 
riments ;  and  Fig.  347  shows  its  position  over  the  lamp. 

A  cover  of  white  paper  prevents  access  of  dust  without  retard- 
ing the  process,  but  care  must  be  taken  that  the  contents  of  the 
vessel  be  not  ejected  against  it,  thus  causing  a  loss. 

In  evaporating  to  dryness,  towards  the  end  of  the  process  the 
flame  must  be  so  managed  as  to  impart  a  uniform  heat  to  all 
parts  of  the  thickened  solution.  The  interposition  of  a  very 
thin  plate  of  sheet-iron  between  the  flame  of  the  lamp  and  the 
bottom  of  the  heating  vessel  is  an  additional  means  of  preventing 
spirting.  These  precautions  and  constant  stirring  will  prevent 
the  loss  of  particles,  which  is  liable  to  occur  upon  the  disengage- 
ment of  the  last  portions  of  liquid.  If  the  liquid  drops  a  powder 


472  CRYSTALLIZATION. 

during  the  operation,  the  vessel  must  be  inclined;  and  in  order 
to  prevent  spirting,  heated  above  the  deposit. 

A  platinum  spatula  is  a  very  useful  implement  for  detaching 
any  efflorescent  matter  which  may  travel  up  the  sides  of  the 
vessel. 


CHAPTER  XXIII. 

CRYSTALLIZATION. 

WHEN  a  body,  in  the  act  of  passing  from  a  liquid  or  gaseous  to 
a  solid  state,  arranges  itself  in  symmetrical  forms,  the  process  is 
termed  crystallization,  and  the  parts  of  the  body  so  aggregated 
are  called  crystals. 

By  this  process  we  can  separate  crystallizable  from  amorphous 
substances  dissolved  in  the  same  menstrua,  purify  crystals  from 
foreign  and  coloring  matters,  and  in  qualitative  examinations,  be 
enabled  to  determine  the  composition  of  bodies  by  a  reference  to 
the  characteristics  of  figure. 

The  modes  of  crystallization  are  by  FUSION,  SUBLIMATION, 
SOLUTION,  and  CHEMICAL  REACTION. 

Crystallization  by  Fusion. — Sulphur,  lead,  bismuth,  tin,  anti- 
mony, silver,  numerous  alloys,  anhydrous  salts,  and  other  fusible 
substances  which  are  unalterable  by  heat,  are  crystallizable  by 

FUSION. 

To  this  end  they  are  melted  at  the  lowest  possible  temperature, 
and  allowed  to  cool  very  gradually.  As  soon  as  a  crust  forms 
upon  the  top,  which  may  be  readily  seen  by  the  surface  becoming 
furrowed,  it  must  be  pierced  with  a  rod,  and  the  still  fluid  por- 
tion decanted  with  sufficient  dexterity  to  prevent  it  from  cooling 
during  the  process,  and  at  the  same  time  from  injuring  the 
crystals  coating  the  interior  of  the  vessel. 

The  liquid  matter  should  be  placed  so  as  to  be  free  from  all 
vibration.  The  greater  the  mass  of  the  material  and  the  more 
slowly  it  is  cooled,  the  more  voluminous  and  better  defined  will 
be  the  crystallization. 

Crystallization  by  Sublimation. — Volatile  solids,   as  iodine, 


CRYSTALLIZATION  FROM   SOLUTION.  473 

camphor,  several  metallic  chlorides  and  mercurial  compounds, 
arsenic,  benzoic  acid,  iodide  of  lead,  &c.,  when  heated  as  directed 
in  SUBLIMATION,  yield  vapors  which,  in  cooling,  take  the  form  of 
crystals. 

Crystallization  from  Solution.— When  it  is  desired  to  obtain 
a  substance  in  crystals,  it  must  first  be  liquefied  or  made  into  a 
SOLUTION  with  an  appropriate  liquid.  If,  after  making  the  solu- 
tion, there  be  any  insoluble  residue,  it  must  be  separated  by 
FILTRATION  ;  and  subsequently,  if  the  solution  is  capable  of  de- 
colorization  by  such  means,  it  should  be  boiled  with  a  small  portion 
of  clean  bone  or  ivory  black,  and  again  filtered.  As  it  is  the 
almost  universal  law  that  heat  increases  the  solvent  power  of 
bodies,  the  solution  should  generally  be  made  and  clarified  at  the 
boiling-point,  so  that  the  excess  of  matter  taken  up  at  the  high 
temperature  may  separate  on  cooling  in  the  form  of  crystals. 

So  long  as  a  solution  is  dilute  it  yields  no  crystals ; — these 
latter  are  only  formed  when  the  containing  liquid  is  supersatu- 
rated, or,  in  other  words,  holds  more  than  it  can  retain  in  fluid 
form ;  and,  consequently,  in  diminishing  the  quantity  of  the 
liquid  by  EVAPORATION,  we  increase  the  density  of  that  which 
remains,  and  hence,  upon  cooling,  it  deposits  that  excess  of  the 
dissolved  substance,  which  it  only  held  by  virtue  of  its  compa- 
ratively high  temperature. 

Some  substances  are  so  easily  soluble,  and  to  such  an  un- 
limited extent,  that  their  solutions  form  crystals  immediately 
upon  cooling;  others  again  are  taken  up  with  such  difficulty, 
even  at  high  heats,  unless  in  large  bulks  of  liquid,  that  although 
exposed  to  prolonged  ebullition,  they  require  to  be  evaporated  in 
order  to  separate  what  has  been  dissolved.  As  the  mode  of 
evaporating  has  an  important  influence  upon  the  form  and  size 
of  crystals,  we  give  some  hints  as  to  the  proper  manner  of  per- 
forming it. 

If  large  and  well-defined  crystals  are  required,  the  solution 
should  be  subjected  to  spontaneous  evaporation,  for  the  more 
slow  and  uniform  the  concentration,  the  more  regular  and  gradual 
will  be  the  superposition  of  material  required  to  make  distinct 
and  large  crystals.  A  slight  addition  of  solution  of  gelatin  will, 
in  some  instances,  it  is  said,  give  the  crystals  the  form  of  plates, 
as  in  the  case  of  boracic  acid. 


474  CRYSTALLIZATION. 

The  solution  should  be  removed  from  the  fire  as  soon  as  drops, 
withdrawn  by  a  glass  rod  and  deposited  upon  a  watch-glass  or 
clean  spatula,  give  small  crystals  upon  cooling.  If,  however,  a 
very  dense  crystallization  is  required,  the  concentration  may  be 
continued  until  a  pellicle  forms  upon  the  top,  but  then  the  solidi- 
fied masses  are  confused  and  less  brilliant.  These  essays  indi- 
cate that  the  liquid  is  evaporated  to  a  point  at  which.it  cannot 
retain  all  of  its  soluble  matter.  The  vessels  are  then  placed 
aside  to  cool  gradually  and  uniformly,  that  the  excess  may  crys- 
tallize out  of  the  liquid.  The  temperature  should  be  regular,  for 
slight  variations  may  alter  the  form  of  the  crystals. 

Bodies  equally  soluble  in  cold  and  hot  water,  as  well  as  those 
which  are  deliquescent,  require  a  prolonged  evaporation,  as  they 
only  crystallize  from  very  dense  solutions. 

When  the  liquid  is  to  be  converted  wholly  into  solid,  then  the 
process  is  termed  granulation,  and  is  practised  by  concentrating 
it  to  a  syrupy  consistence,  removing  the  vessel  from  the  fire  and 
stirring  it  constantly  until  the  mass  has  cooled  into  granules. 
This  mode  is  adapted  for  purifying  pearl-ash  and  converting  it 
into  sal  tartar,  and  also  for  graining  brown  sugars. 

If  the  liquid,  evaporated  as  above  directed,  becomes  colored  or 
murky  during  the  process  from  partial  decomposition,  it  may  be 
treated  with  bone-black,  and  again  filtered  into  a  capsule,  or  other 
vessel,  previously  warmed  by  a  rinsing  with  hot  water,  so  as  to 
prevent  confused  crystallization  from  sudden  contact  with  its  cold 
surfaces.  Blue  stoneware  capsules  are  far  better  than  porcelain 
capsules  or  glass  beakers,  as  they  are  not  only  more  durable,  but 
by  the  roughness  of  their  interior  surfaces  far  more  promotive  of 
crystallization.  Stone  basins  for  this  purpose,  called  crystallizers, 
are  made  of  all  sizes,  in  depth  greater  than  in  breadth,  and  with 
a  lip  to  facilitate  the  separation  of  the  residual  liquid  from  the 
crystals.  This  residual  liquid,  called  the  mother  water,  is  usually 
returned  to  the  evaporating  vessel  to  be  further  concentrated  for 
the  production  of  a  new  crop  of  crystals,  particularly  if  the  liquid 
has  been  homogeneous. 

The  first  crop  of  crystals  is  generally  purer  than  subsequent 
ones,  but  may  still  not  be  sufficiently  free  from  foreign  salts  and 
other  matters,  and,  therefore,  require  to  be  dissolved  anew  and 
recrystallized  as  at  first.  The  pure  crystals  are  drained  of  their 


PURIFICATION    OF   CRYSTALS.  475 

mother  water  by  inclining  the  crystallizer  over  the  evaporating 
vessel  long  enough  to  allow  all  of  the  fluid  to  run  off  at  the  spout. 
The  crystals  are  then  removed  with  a  spatula  and  transferred  to 
a  drainer,  which  is  generally  made  of  porcelain  or  earthenware, 
and  after  the  form  of  a  saucer  or  funnel,  Figs.  382,  383,  accord- 
Fig.  382. 


ing  to  the  quantity  and  nature  of  the  crystals.  Thence,  they  are 
subsequently  removed  to  the  drying-frame.  In  the  first  crystal- 
lization, the  mass  of  impure  crystals  is  drained  upon  a  filter, 
and,  if  necessary  to  free  them  from  syrupy  or  dirty  liquid,  en- 
closed in  a  cloth  and  pressed  (Fig.  375).  Sometimes,  especially 
when  the  crystals  are  no*  very  soluble,  they  may  be  drenched, 
while  upon  the  filter  or  drainer,  with  cold  water,  which  carries 
away  much  soluble  impurity.  This  solution,  if  valuable,  may  be 
mixed  with  the  mother  waters,  and  the  whole,  after  being  trans- 
ferred to  the  evaporating  vessel,  be  concentrated  and  again  crys- 
tallized. The  crop  thus  obtained  is  very  impure,  and  requires  to 
be  drained  on  a  cloth  and  pressed,  and  subjected  to  as  many 
treatments  with  bone-black,  and  renewed  crystallizations,  as  are 
required  to  remove  all  color.  It  must  be  remembered,  however, 
that  bone-black  is  only  used  when  the  coloring  substance  is  or- 
ganic, and  when  the  characteristic  color  of  the  crystals  is  light, 
for  it  has  no  blanching  action  upon  either  organic  or  unorganized 
bodies  which  are  naturally  tinted. 

In  recrystallizations,  only  as  much  water  as  is  necessary  to 
effect  solution  should  be  used,  so  that  the  mother  waters  may  be 
as  small  in  quantity  as  possible.  The  last  mother  waters  being 
incapable  of  yielding  any  more  crystals,  may,  in  some  processes, 
be  reserved  for  other  purposes ;  as,  for  instance,  making  new 
compounds.  Thus,  for  example,  the  mother  waters  of  iodide  of 
potassium  may  be  used  to  precipitate  iodide  of  mercury  from  the 
bichloride  of  that  metal,  or  of  lead  from  the  nitrate  of  lead,  and 


476  CRYSTALLIZATION. 

those  of  chloride  of  barium  to  obtain  carbonate  of  baryta,  upon 
the  addition  of  carbonate  of  soda. 

Sometimes,  however,  crystallization  is  resorted  to  for  the  sepa- 
ration of  one  substance  mixed  with  others,  which  are  variably 
soluble  in  the  same  liquid,  and  which  do  not  crystallize  together, 
but  separate  from  the  solvent  at  different  stages  of  concentration. 
In  such  case,  the  mother  waters  may  contain  one  or  more  of  the 
other  components  of  the  original  substance,  and  hence  are  not 
useful  for  forming  new  compounds  by  PRECIPITATION.  After 
the  separation  of  each  to  the  fullest  extent  by  crystallization,  at 
different  temperature,  the  residue  of  liquor,  unless  it  be  of  great 
value,  may  be  thrown  away. 

As  before  said,  gradual  evaporation  at  a  uniform  temperature, 
and  a  perfect  repose  of  the  concentrated  solution,  give  the  most 
perfect  crystals.  S8me  solutions,  however,  crystallize  less  readily 
than  others,  and  remain  even  days  and  weeks  without  exhibiting 
any  sign  of  such  tendency.  In  such  cases,  it  is  advisable  to 
agitate  the  mass  slightly,  or  to  stir  it  gently  with  a  glass  rod. 
This  manipulation  arouses,  as  it  were,  the  molecules  from  their 
inertia,  and  frequently  determines  speedy  crystallization.  The 
resulting  crystals  are  generally,  however,  confused  and  dimi- 
nutive. 

To  obtain  large  crystals  from  a  solution  which  is  slow  in  depo- 
siting them,  it  is  sometimes  proper  to  add  nuclei  to  the  cold 
solution,  these  consisting  of  well-formed  large  crystals  of  the 
same  substance.  As  the  solution  increases  its  density  by  spon- 
taneous evaporation,  the  nuclei  assume  a  large  size ;  but  in  order 
that  their  enlargement  may  be  uniform  throughout,  they  must  be 
turned  daily,  so  that  the  accumulation  of  matter  may  take  place 
on  all  their  surfaces. 

This  mode,  as  practised  in  the  arts,  is  somewhat  modified. 
The  deposition  surfaces  are  increased  by  inserting  in  the  solution 
strings  as  nuclei.  When  one  solution  is  thus  exhausted  of  its 
soluble  matter,  the  strings  with  their  surrounding  crystals  are 
transferred  to  as  many  fresh  vats  consecutively  as  are  required 
to  give  the  crystals  the  proper  size.  In  this  manner,  blue 
vitriol,  prussiate  of  potash,  tartar  emetic,  and  rock  candy  are 
crystallized. 

When  the  twine  loops  are  replaced  by  slender  twigs  or  branches 


CRYSTALLIZATION    BY    CHEMICAL    REACTION.  477 

of  wood,  and  the  crystals  are  deposited  in  fine  flakes  from  bulky 
solutions,  the  process  is  termed  arborization. 

Examples  of  arborization,  where,  however,  crystallization  is 
accompanied  by  chemical  or  voltaic  action,  are  furnished  by  the 
various  metallic  trees,  which  are  clusters  of  metallic  flakes  or 
crystals  precipitated  upon  the  surface  of  a  dissimilar  metal  sus- 
pended in  their  solution. 

Payen  has  suggested  the  following  method  of  increasing  the 
size  and  regularity  of  the  crystals,  and  especially  those  obtained 
from  substances  soluble  with  difficulty. 

In  the  apparatus  employed,  the  liquid  circulating  through  one 
part  dissolves  the  substance  to  be  crystallized,  and  deposits  it  in 
crystalline  forms  in  another  and  cooler  part. 

"  The  arrangement  consists  of  a  flask  or  tubulated  receiver, 
surmounted  by  another  similar  vessel,  the  two  being  adjusted  by 
the  necks,  and  communicating,  at  the  lateral  opening,  by  tubes, 
the  one  with  the  top  and  the  other  with  the  bottom  of  a  vessel 
placed  at  some  distance.  The  inverted  receivers  are  both  filled 
with  the  substance  to  be  dissolved,  and  the  whole  of  the  apparatus 
with  the  solvent.  Heat,  derived  from  a  constant  and  uniform 
source,  is  applied  to  the  receivers,  by  which  a  continual  circula- 
tion of  the  liquid  is  maintained,  and  this  being  saturated  in  the 
most  heated  part  of  the  apparatus  is  conveyed  to  the  cooler  part, 
where  the  deposition  takes  place." 

Crystallization  may  thus  be  made  to  take  place  slowly  and 
regularly.  Payen  obtained,  by  this  means  and  the  use  of  benzole 
as  the  solvent,  crystals  of  sulphur  one  hundred  times  larger  than 
those  formed  in  the  usual  way. 

Crystallization  by  Chemical  Reaction.  —  The  newly-formed 
compounds,  resulting  from  chemical  reaction,  frequently  assume 
the  crystalline  shape.  Thus,  for  example,  antimony  roasted 
in  contact  with  air  forms  crystals  of  antimonious  acid ;  chlorine 
acting  upon  phosphorus  produces  crystals  of  perchloride  of  phos- 
phorus. So,  likewise,  crystals  of  bicarbonate  of  potassa  are 
produced  when  carbonic  acid  is  passed  through  a  concentrated 
solution  of  carbonate  of  potassa. 

Silver  displaced  from  its  solutions  by  zinc  forms  a  crystalline 
deposit.  Sulphate  of  lime  precipitated  by  alcohol  from  its 
aqueous  solution  also  falls  in  crystals.  Morphia,  also,  and  other 


478  DESICCATION. 

crystalline  alkaloids,  may,  in  like  manner,  be  precipitated  by 
decomposing  their  solutions  with  ammonia. 


CHAPTER  XXIV. 

DESICCATION. 

THE  desiccation  of  a  substance  consists  in  the  expulsion  of  its 
"moisture."  The  term  moisture  is  used  only  in  reference  to 
that  variable  amount  of  water,  and  sometimes,  though  rarely,  of 
other  liquids,  which  it  may  have  absorbed,  or  otherwise  retained 
in  a  state  of  mechanical  union.  The  combined  water,  or  that  of 
crystallization,  of  which  many  bodies  are  in  part  constituted, 
exists  in  an  entirely  different  form,  and  is  not  usually  to  be  ex- 
pelled when  the  drying  is  preliminary  to  analysis.  When,  how- 
ever, it  is  desired  to  dehydrate  a  body  entirely,  this  latter  water 
of  combination  is  also  to  be  dissipated. 

The  means  of  desiccation  are  various,  and  differ  with  the  nature 
of  the  substance  to  be  dried,  its  quantity,  and  alterability  by  heat 
and  exposure. 

DESICCATION  OF  SOLIDS. — Undecomposable  salts  and  any  sub- 
stances unalterable  by  air  or  heat,  may  be  dried  by  FUSION.  If 
the  amount  of  moisture  is  to  be  determined,  the  crucible  and  its 
contents  should  be  weighed  before  and  after  the  operation,  the 
loss  expressing  the  weight  of  water  expelled.  Those  bodies, 
however,  which  will  not  bear  the  heat  necessary  for  fusion,  can 
be  desiccated  by  EVAPORATION  to  dryness  in  a  capsule, — care 
being  taken  to  renew  surfaces  by  constant  stirring. 

Those  saline  matters  which  readily  yield  all  their  water  by 
exposure  may  be  reduced  to  powder  or  effloresced  by  subjecting 
them  in  thin  layers  to  a  draught  of  dry  air,  which,  if  necessary, 
may  be  moderately  heated.  For  this  purpose,  as  well  as  for  that 
of  drying  crystals  which  do  not  effloresce,  it  is  necessary,  in 
manufacturing  laboratories,  to  have  a  special  apartment.  This 
room  should  be  smoothly  plastered  within,  and  need  not  be  of 
large  size.  As  a  means  of  ventilation  its  opposite  sides  are 
pierced  with  small  holes,  which,  to  prevent  the  admission  of  dirt, 


DESICCATION    OF   SOLIDS. 


479 


are  covered  with  wire  gauze.  The  interior  is  fitted  with  trellis 
shelves  for  the  support  of  the  wooden  frames,  stretched  over  with 
white  muslin,  and  upon  which  the  substance  rests  between  or 
upon,  as  may  be  required,  folds  of  bibulous  white  paper.  The 
heat  is  communicated  by  sheet-iron  flues  proceeding  from  a  stove 
placed  outside  of  the  enclosure,  or  by  means  of  steam-pipes  fed 
by  the  generator,  Fig.  15.  The  temperatures  should  range  from 
75°  to  110°  F. 

This  apartment  is  also  useful  for  pharmaceutical  purposes,  for 
drying  plants,  roots,  seeds,  woods,  &c.  They  may  either  be  sus- 
pended or  spread  in  thin  layers  upon  frames,  and  repeatedly 
turned  for  the  purpose  of  exposing  fresh  surfaces. 

The  air-chamber,  p.  40,  may,  to  a  limited  extent,  be  made  to 
replace  this  apartment,  and  in  an  experimental  laboratory  it  is, 
together  with  the  means  mentioned  in  this  chapter,  sufficient  for 
all  purposes. 

As  the  salts  effloresced  as  above  still  retain  a  little  water,  they 
require  to  be  repeatedly  pressed  between  the  folds  of  white  paper 
until  dampness  ceases  to  be  imparted  to  them.  Sometimes  a 
previous  trituration  is  necessary  to  facilitate  the  process. 

Filters  containing  precipitates,  after  careful  removal  from  the 
funnel  and  compression  between  the  folds  of  bibulous  paper,  may 
be  further  dried  in  the  same  manner.  Those,  however,  which 
contain  the  results  of  analytic  experiments  require  more  careful 
manipulation.  For  their  treatment  a  copper-plate  oven  is  often 
used.  It  consists  (Fig.  384)  of  a  brass  soldered  copper  box  7  X 

Fig.  384. 


9  inches,  enveloped  by  a  steam-tight  jacket,  in  the  door  of  which 
are  vent-holes  for  change  of  air.  The  water,  or  the  olive  oil 
which  is  used  if  the  substance  requires  a  heat  higher  than  212° 
for  its  desiccation,  is  poured  through  the  centre  aperture  at  the 


480  DESICCATION. 

top,  but  must  not  more  than  half  fill  the  jacket.  The  lateral 
opening  is  for  the  reception  of  a  thermometer,  which  is  adjusted 
by  means  of  a  perforated  cork,  for  facilitating  the  regulation  of 
the  temperature.  ^.^ 

The  watch-glasses,  plates,  or  capsules,  in  which  the  substances 
to  be  dried  are  placed,  rest  upon  the  perforated  shelves  in  the 
interior. 

The  thermometer  will  indicate  with  precision  the  temperature 
of  the  bath,  and  care  must  be  taken  that  the  latter  be  not 
allowed  to  exceed  the  degree  above  which  the  body  to  be  dried 
decomposes. 

If  the  substance  to  be  dried  is  not  alterable  by  temperatures 
above  212°  F.  to  300°,  they  may  be  expeditiously  dried  in  the 
air-box,  Fig.  385,  described  below,  which  differs  from  the  preced- 

:  •'      Fig.  385. 


ing  in  receiving  its  heat  direct  from  the  flame,  and  without  the 
intermedium  of  a  bath.  It  consists  of  a  strong  brass  box,  6  to  8 
inches  in  width  and  depth,  with  a  corresponding  height.  In  the 
centre  of  the  top  is  a  circular  opening,  in  which  a  thermometer  is 
adjusted  by  means  of  a  cork.  A  wire  stand  in  the  interior  serves 
as  a  support  for  the  containing  vessels,  and  allows  the  drying  of 
filters  in  funnels,  when  it  may  be  inexpedient  to  remove  them. 
Circular  holes,  in  the  lower  and  upper  parts  of  the  sides,  create 


DESICCATION  BY  BATHS.  481 

a  circulation  of  air  through  the  box,  and  thus  promote  evapo- 
ration. 

Rammelsberg's  air-bath,  Fig.  386,  is  very  similar  to  the  pre- 
ceding, but  allows  the  use  of  a  tall  chimney, 
which,  by  determining  a  powerful  draught 
through  the  chamber,  greatly  expedites  the 
drying  process.  It  consists  of  a  cylindrical 
copper  box,  six  inches  high  by  four  inches 
wide,  and  has  a  loose  cover,  in  which  is  ad- 
justed a  thermometer  for  regulating  the  tem- 
perature. Rising  from  the  cover  opposite  to 
the  thermometer  is  the  chimney,  which  should 
have  a  height  of  9  to  12  inches.  One  or  two 
circular  openings,  at  the  circumference  and  at 
the  base  of  the  cylinder,  are  necessary  for  the 
admission  of  air. 

A  perforated  diaphragm,  midway  in  the 
interior,  serves  as  a  support  for  the  crucibles, 
watch-glasses,  capsules,  funnels,  and  other 
vessels  containing  the  matters  to  be  dried. 

Kemp's  Thermostat. — When  street  gas  is  used  for  heating  the 
air-baths,  it  is  apt  to  give  unequal  temperatures,  owing  to  the 
variable  pressure  upon  the  service-pipes  at  different  times.  To 
prevent  this  annoyance,  Kemp  has  devised  a  most  convenient  and 
efficient  apparatus,  which  he  properly  designates  a  Thermostat,  as 
it  regulates  the  supply  of  the  gas  to  the  burner,  and  of  course 
the  amount  of  heat  thus  applied  to  the  substance  under  process, 
thereby  insuring  a  constant  temperature  for  any  length  of  time. 

This  simple  and  ingenious  apparatus  will  be  found  serviceable 
for  all  operations  requiring  a  prolonged  temperature  of  great  uni- 
formity. The  author  used  it  successfully  in  promoting  tedious 
fermentations,  artificial  incubation,  and  for  obtaining  products  of 
the  decomposition  of  organic  bodies  at  fixed  temperatures.  The 
use  of  mercury  renders  it  available  only  for  temperatures  below 
the  boiling-point  of  that  metal ;  but  by  making  the  instrument 
of  iron  and  substituting  fusible  alloys  for  mercury,  it  becomes 
applicable  for  higher  degrees. 

The  instrument  itself,  shown  in  the  following  drawing,  consists 
of  an  air-thermometer  B  A  of  glass,  and  containing  mercury  in 

31 


482 


KEMP'S   THERMOSTAT. 


the  lower  part  of  the  bulb  A,  and  a  portion  of  the  stem  B.  A 
tube  of  smaller  diameter,  as  seen  in  the  figure,  passes  down  the 
axis  of  the  tube  B,  the  annular  space  being  made  air-tight  by  a 

./'•J..V'*"  J'1  «  Fig.  387. 


small  brass  stuffing-box  B,  which  enables  it  to  be  retained  at  any 
required  elevation.  An  air-tight  connection  is  made  at  c  with  a 
piece  of  flexible  caoutchouc  tube,  communicating  with  the  service- 
pipe  by  means  of  a  gallows-screw.  The  gas  entering  through 
this  channel  passes  into  the  long  stem  of  the  thermometer,  and 
thence  to  the  burner  D. 

In  using  the  instrument,  the  bulb  A  must  be  immersed  in  the 
water-bath  with  the  substance  under  examination,  if  that  means 
of  heating  is  employed ;  and,  in  the  case  of  an  air-bath  or  hot 
press,  it  must  be  placed  in  immediate  vicinity  of  the  substance, 
so  as  to  produce  an  equilibrium  of  temperature  between  the  air 
in  the  bulb  and  the  surrounding  atmosphere. 

The  inventor  thus  explains  its  mode  of  operation.  Supposing, 
for  example,  that  it  is  required  to  keep  an  object  at  a  tempera- 
ture of  100°  F.,  then  the  bulb  of  the  instrument  being  placed 

- 


KEMP'S  THERMOSTAT.  488 

contiguous  to  the  object,  a  free  supply  of  gas  is  allowed  to  flow 
through  the  burner,  and  a  flame  ignited.  The  heat  soon  begins 
to  act  upon  the  air  in  the  bulb,  causing  it  to  expand  and  force 
the  mercury  up  the  stem  B ;  and  when  it  is  found,  by  the  use  of 
a  common  thermometer,  that  the  heat  has  risen  to  the  required 
degree,  the  inner  and  smaller  tube  is  to  be  pushed  down  until  its 
lower  extremity  reaches  below  the  surface  of  the  mercury.  This 
would,  of  course,  cause  the  flame  to  be  extinguished ;  but,  as  the 
preventive  of  this  occurrence,  a  small  hole  is  bored  through  the 
inner  tube  above  the  extremity,  to  permit  the  transit  of  a  small 
quantity  of  gas  to  the  burner.  As  the  passage  of  the  gas  is  now 
interrupted,  the  source  of  heat  is  withdrawn,  and  the  cooling  in- 
fluence of  the  surrounding  air  then  causes  the  air  contained  in  A 
to  contract,  and  the  mercury  in  B  to  sink,  and  leave  the  end  of 
the  internal  tube  uncovered.  A  free  channel  for  the  gas  is  thus 
opened,  so  that,  as  combustion  proceeds,  the  temperature  would 
again  rise  and  cut  off  the  supply ;  but,  in  a  short  time,  these  two 
opposing  forces  reach  an  equilibrium,  and  scarcely  any  variation 
in  the  size  of  the  flame  occurs.  To  insure  perfect  contact  of  the 
end  of  the  inner  tube  with  the  mercury,  the  former,  to  the  extent 
of  a  half  inch,  is  made  of  platinum,  and  amalgamated  by  dipping 
it  into  a  liquid  amalgam  of  sodium  and  mercury. 

Westly  proposes  to  improve  Kemp's  instrument  by  cutting  or 
grinding  off  the  inner  tube  c  on  one  side,  so  as  to  form  a  long, 
narrow  slit  in  place  of  the  small  hole.  This  modification  prevents 
the  sudden  jerks  with  which  the  aperture  otherwise  opens  and 
closes. 

If  the  extremity  of  the  inner  tube  be  formed  into  a  cone,  like 
an  inverted  funnel,  and  then  a  portion  of  the  side  cut  off,  the  area 
of  the  aperture  for  the  passage  of  the  gas  will  form  a  parabola, 
or  hyperbola,  as  required,  by  which  the  flow  of  gas  may  be  regu- 
lated with  great  precision  to  the  desired  temperature,  and  in  any 
ratio  that  is  needed.  To  insure  metallic  contact  with  the  mer- 
cury, the  interior  of  the  tube  may  be,  for  a  short  length,  electro- 
typed  with  platinum. 

According  to  Wetherill,  a  glass  tube  may  be  made  to  replace 
that  of  platinum  by  drawing  it  out  at  the  end  in  such  a  manner 
that  the  tip,  to  the  length  of  three-quarters  of  an  inch,  shall  have 
a  diameter  of  one-sixteenth  of  an  inch.  The  quarter  inch  of  the 


484 


WETHERILL'S  THERMOSTAT. 


end  immediately  behind  the  tip  is  carefully  filed  down  with  an 
angular  file,  so  as  to  produce  a  fine  slit.  By  this  slight  modifica- 
tion, the  extremity  of  the  tube  comes  in  the  centre  of  the  rising 
column  of  mercury,  which  closes  it  accurately. 

The  drawing  presents  Wetherill's  adaptation  of  the  thermostat 
to  an  air-bath ;  the  tube  being  shown  at  2  in  full  size.  The  hole 
a,  through  which  the  gas  passes  to  the  burner  when  the  extremity 
Js  closed,  must  be  only  large  enough  to  admit  sufficient  gas  to 
prevent  the  extinction  of  the  light.  The  burner  employed  is  in 
the  form  of  a  cross,  and  consists  of  two  pieces  of  brass  tube  closed 
at  the  end,  and  united  by  brazing  in  such  a  manner  as  to  leave  a 
free  communication  throughout  the  bores.  The  holes  for  the 
exit  of  the  gas  are  drilled  into  the  upper  surface  with  a  needle. 
A  leaden  weight  E,  cast  at  the  centre  of  the  cross,  serves  to  give 
steadiness  to  the  burner,  and  at  the  same  time  sufficient  elevation 
to  promote  draught  of  air  beneath.  The  air-bath  rests  upon  a 
box  of  four  inches  height,  which  encloses  the  burner;  and  a 
movable  opening  gives  access  to  the  interior,  as  may  be  necessary  ? 
to  light  or  examine  the  flame. 

"Fig.  388  represents  an  arrangement  for  drying  substances  in 

Fig.  388. 


Fig.  389. 


a,  current  of  dry  air  produced  by  the  efflux  of  water.  For  this 
purpose  a  known  weight  of  the  substance  is  in- 
troduced into  the  small  bent  glass  tube  (Fig. 
389),  which  has  also  been  weighed ;  the  body 
of  this  tube  being  then  plunged  into  a  copper 
water-bath  5,  charged  with  a  saturated  solu- 
tion of  common  salt,  it  is  kept  in  its  place  by 

a  cover  furnished  with  two  apertures  for  the  arms  of  the  drying- 


DESICCATION   OP  EASILY  ALTERABLE   SUBSTANCES.         485 

tube ;  the  wider  arm  is  united  by  means  of  bent  tubes  and  a 
caoutchouc  connector  with  the  U-shaped  tube,  and  containing 
fragments  of  chloride  of  calcium,  and  the  narrow  end  is  con- 
nected with  a  bent  tube,  which  passes  through  the  cork  of  the 
bottle  A  nearly  down  to  its  bottom.  This  cork  must  fit  the  bottle 
perfectly  air-tight,  and  all  the  joints  and  connections  of  the  whole 
apparatus  must  be  perfect.  The  bottle  A  is  filled  with  water, 
which,  on  turning  the  stop-cock  s,  flows  out  in  a  small  stream,  its 
place  being  supplied  by  the  air  drawn  through  c,  and  which 
becomes  dried  during  its  passage  through  the  chloride  of  calcium, 
tube  b.  The  bath  is  charged  with  water,  a  saturated  solution  of 
common  salt,  or  of  chloride  of  calcium,  according  to  the  degree 
of  heat  required,  and  it  is  kept  boiling  by  means  of  a  spirit  or 
gas  lamp  placed  underneath." 

Desiccation  of  easily  Alterable  Substances. — It  has  already 
been  said  that  the  power  of  absorbing  and  retaining  moisture 
varies  in  different  bodies.  This  property  renders  the  use  of 
those  which  have  it  in  the  greatest  degree  available  for  the  drying 
of  others  which  are  deficient  in  it.  The  substances  subjected  to 
this  mode  of  drying  are  mostly  organic  bodies,  and  those  readily 
alterable  by  heat  or  exposure,  but  which  yield  their  moisture 
much  below  212°  F. 

A  very  simple  method  of  accomplishing  this  kind  of  desiccation 
is  to  suspend  the  substance  in  a  beaker  glass 
b,  over  a  large  volume  of  sulphuric  acid  0, 
Fig.  390.  The  rim  of  the  glass  is  ground  for 
the  purpose  of  making  a  tight  joint  with  the 
ground-glass  plate  cover  d,  which  has  a  hole 
in  the  centre  for  the  support  of  a  cork,  with 
the  tray  and  wires  e  suspended  to  it.  Upon 
this  tray  rests  the  watch-glass  or  capsule  c, 
which  contains  the  substance  under  process. 
The  rim  should  be  greased  previous  to  placing 
the  cover  upon  it,  so  as  to  render  the  connection  air-tight. 

The  sulphuric  acid  absorbs  the  moisture  as  fast  as  it  arises 
from  the  substances,  and  thus  maintains  constant  dryness  of  the 
internal  atmosphere.  When  the  substance  has  ceased  to  lose 
weight,  the  operation  is  finished. 


486         DESICCATION   OF   EASILY  ALTERABLE   SUBSTANCES. 

Another  arrangement  for  the  same  purpose  consists  of  a  large 
bell  glass,  fitting  accurately  upon  a  ground-glass  plate  or  bed. 
Within  is  a  shallow  saucer  6,  containing  dry  chloride  of  calcium, 
strong  sulphuric  acid,  or  other  highly  absorbent  material,  and 
over  it  a  perforated  glass  support  «,  upon  which  rest  the  capsules, 
crucibles,  beaker,  watch-glass,  or  other  containing  vessels.  Fig. 
391  exhibits  the  whole  arrangement.  The  rim  of  the  bell,  as  also 

Fig.  391. 


that  part  of  the  plate  which  it  touches,  are  to  be  greased,  in  order 
to  make  the  joint  hermetical.  The  material  thus  exposed  to  dry 
air  continues  to  lose  moisture  until  all  has  been  expelled,  or  until 
the  absorbent  matter  has  become  saturated;  in  such  case  the 
latter  must  be  replaced  with  a  fresh  quantity. 

By  substituting  the  bed  of  an  air-pump  for  the  glass  disk  as  a 
support  for  the  other  parts  of  the  apparatus,  otherwise  arranged 
exactly  as  above  described  and  shown  in  the  figure,  and  increasing 
the  evaporation  by  exhausting  the  air,  desiccation  proceeds  much 
more  rapidly  and  effectually.  A  partial  vacuum  being  thus  pro- 
duced the  drying  substance  liberates  its  aqueous  vapor  freely, 
new  portions  being  given  off  as  soon  as  those  which  preceded 
them  are  condensed  by  the  absorbent  in  the  saucer,  which  is 
usually,  in  these  cases,  fused  chloride  of  calcium  or  strong  sul- 
phuric acid,  those  agents  absorbing  watery  vapors  perhaps  to  a 
greater  extent  than  any  other.  The  process  is  thus  continued 
until  complete  desiccation  of  the  substance  and  saturation  of  the 
absorbent  material  ensue,  the  latter  being  renewed  as  often  as 
may  be  necessary. 


DESICCATION  IN  VACUO, 


487 


Fig.  392. 


If  the  eliminated  vapors  are  corrosive,  it  is  advisable  to  modify 
the  arrangement,  so  that  they  may  be  neutralized  as  fast  as  gene- 
rated, otherwise  the  metallic  surfaces  of  the  air-pump  will  be 
injured.  A  suitable  apparatus  is  shown  in  Fig.  392.  It  is  an 
inverted  bell  glass,  fitted  at  its  neck  with  a 
stop-cock,  by  which  it  connects  with  a  tube 
containing  pumice-stone  impregnated  with 
acid  or  alkali,  according  to  the  nature  of  the 
vapors  to  be  absorbed.  The  substance  to 
be  dried  and  the  absorbent  or  hygroscopic 
body  are  arranged  within  the  bell  in  the 
usual  manner.  The  latter  is  then  greased 
at  its  edges,  hermetically  covered  with  a 
ground-glass  plate,  and  exhausted  of  air  by 
a  syringe  coupled  with  the  further  end  of  the  drying  or  chlorcal- 
cium  tube  e. 

By  having  a  bed  of  ground-glass  instead  of  metal,  and  de- 
tached from  the  pump  or  syringe,  and  made  to  communicate  with 
it  by  flexible  lead  pipe  and  gallows-screws  only  when  exhaustion 
is  required,  an  apparatus  is  made,  which,  as  represented  in  Fig. 
391,  becomes  available  for  all  the  purposes  of  evaporation  and 
desiccation. 

Another  mode  of  drying  alterable  and  fixed  substances  in  vacuo 
is  shown  by  the  arrangement,  Fig.  393,  which  effects  a  repeated 
change  of  air.  It  consists  of  a  copper  cylinder  box,  soldered 

Fig.  393. 


with  brass,  having  two  apertures  in  its  top,— one,  g,  for  the  re- 
ception of  a  thermometer  by  which  to  regulate  the  temperature, 
and  the  other  for  a  glass  tube  e,  the  recipient  of  the  substance  to 


488  DESICCATION   OF   LIQUIDS. 

be  dried.  This  tube  is  connected  by  means  of  a  smaller  glass 
tube  i,  tightly  adjusted  in  perforated  corks  with  the  chloride  of 
calcium  tube  d,  and  thence  also  with  the  exhausting  syringe  5. 
Heat  being  applied  to  the  bath  by  means  of  a  small  furnace  or 
gas  lamp,  a  partial  vacuum,  is  then  produced  by  several  strokes 
of  the  syringe  piston.  In  a  few  moments  air  is  to  be  admitted 
through  the  cocks  c  and  a,  and  this  exhaustion  and  airing  is  to 
be  repeated  at  occasional  intervals,  the  air  in  its  transit  being 
deprived  of  all  moisture  by  the  chloride  of  calcium.  When  it  is 
desired  to  replace  atmospheric  air  by  carbonic  acid,  hydrogen,  or 
other  gas,  it  may  be  introduced  by  connecting  the  gasometer, 
containing  the  required  gas,  by  suitable  couplings  with  the  same 
apparatus. 

DESICCATION  OF  LIQUIDS. — Desiccation  properly  means  the 
freeing  of  a  body,  capable  of  existing  in  a  dry  state,  from  acci- 
dental moisture.  But,  for  the  sake  of  uniformity  of  description, 
we  have  applied  the  term  also  to  the  separation,  from  fluids,  of 
water,  which  is  the  ordinary  source  of  moisture.  This  is  usually 
done  by  the  agitation  with  the  liquid  of  some  absorbent  material, 
which  either  unites  with  the  water,  forming  a  stratum  of  different 
density  capable  of  being  separated  by  filtration  or  decantation ; 
or  else  combines  with  it  so  firmly  that  the  fluid,  which  is  usually 
more  volatile,  can  be  separated  by  distillation. 

Thus  alcohol  and  other  spirits  are  rectified  by  distillation  over 
carbonate  of  potassa,  chloride  of  calcium,  or  free  lime,  it  being 
only  necessary  to  stop  the  process  as  soon  as  the  liquid  comes 
over  slowly,  which  indicates  that  all  the  pure  spirit  has  passed. 
Agitation  of  ether  with  any  of  the  same  absorbents  produces 
similar  results. 

For  analytic  purposes,  and  in  minute  experiments,  accidental 
moisture  may  be  expelled  from  liquids  less  volatile,  by  exposing 
them  in  open  vessels  under  the  receiver  of  an  air-pump,  as  de- 
scribed for  solids  in  the  preceding  paragraphs. 

DESICCATION  OF  GASES. — Nearly  all  gases  in  the  course  of 
elimination  become  involved  with  more  or  less  moisture,  from 
which  it  is  frequently  desirable  to  separate  them  previous  to  their 
application  to  chemical  reaction.  For  this  purpose  they  are 
passed  over  some  highly  absorbent  material,  such  as  dried  chloride 
of  calcium,  quicklime,  or  sulphuric  acid. 


DESICCATION  OF  GASES.  439 

The  simplest  arrangement  for  the  purpose  is  given  at  Fig.  218 
which  exhbits  a  straight  tube  d  d,  containing  the  dried  chloride' 
of  calcium,  adapted  at  one  end  by  means  of  a  perforated  cork 
with  the  gas  generator  A,  and  at  the  other,  in  like  manner,  with 
a  disengagement-tube  ee.  The  gas  in  its  transit  through  the 
chlorcalcium  tube  is  relieved  of  its  moisture.  This  tube  varies  in 
me  from  half  to  one  inch  diameter,  and  eight  to  twelve  inches 
length,  according  to  the  quantity  of  gas  to  be  desiccated.  The 
chloride  of  calcium  can  be  replaced  by  quicklime,  potassa  or 
pumice-stone  impregnated  with  sulphuric  acid,  as  the  nature  of 
the  gas  may  require ;  but  in  either  case  the  solid  material  should 
be  m  small  lumps.  The  water  formed  during  the  process  collects 
in  this  tube. 

Liebig  uses  the  drying-tube  of  such  a  form  as  is  shown  at  Fig. 
394.     It  differs  from  the  above  in  having  a  bulb,  and  in  being 

Fig.  394. 


drawn  out  at  one  end  to  a  fine 'tube,  thus  leaving  but  one  aper- 
ture to  be  corked.  Lumps  of  absorbent  matter  are  placed  in  the 
bulb,  and  coarse  powder  of  the  same  substance  in  the  long  part, 
each  end  of  which  is  very  loosely  plugged  with  raw  cotton  to 
prevent  the  exit  of  particles. 

For  small  operations,  the  bent  form,  Fig.  395,  is  most  conve- 
nient, as  it  is  easily  adjusted  to  the  mouth  of 
the  bottle  without  the  necessity  of  multiply-  Fig.  395. 

ing  joints.     The  bulbs,  in  these  two  latter       — Qhaaa 
tubes,  serve  also  as  wells  for  the  reception  of     f 
the  condensed  vapor. 

Dumas's  vertical  drying-tube,  designed  for  the  desiccation  of 
large  quantities  of  very  moist  gas,  is  so  constructed  that  the  con- 
densed vapor  instead  of  remaining  in  contact  with  the  pumice, 
and  thus  impairing  its  absorbent  power,  will  be  deposited  in  the 
lower  part.  The  tube  leading  from  the  generating  vessel  is 
adapted  by  means  of  a  perforated  cork  to  a  lateral  tubulure 
at  the  base.  The  disengagement-tube  is  similarly  adapted  to 
the  top. 

The  selection  of  the  drying,  or  hygroscopic  material,  must,  as 


490  DESICCATION   OF  GASES. 

before  said,  be  made  with  a  regard  to  the  nature  of  the  gas ;  thus, 
for  example,  quicklime  should  never,  for  obvious  reasons,  be  used 
for  desiccating  chlorine,  or  other  gases  which  combine  with  it 
chemically ;  for  the  drying  of  nearly  all  such  gases  an  acid  body 
may  be  employed,  and  pumice-stone,  in  lumps  of  about  the  size 
of  half  of  a  pea,  impregnated  with  sulphuric  acid,  is  very  service- 
able, as  it  presents  a  large  extent  of  surface.  For  this  purpose, 
however,  the  pumice  must  be  freed  from  all  the  chlorides  which 
it  contains,  otherwise  the  sulphuric  acid  will  disengage  muriatic 
acid,  possibly  to  the  great  detriment  of  the  gas  which  is  under- 
going drying.  The  best  way  is  to  pulverize  and  moisten  it  with 
sulphuric  acid,  and  subject  it  to  calcination  in  a  crucible.  When, 
after  constant  stirring,  it  ceases  to  disengage  acid  vapors,  the 
operation  is  finished. 

Anhydrous  phosphoric  acid  is  also  occasionally  employed  as  a 
drier,  but  only  in  very  nice  experiments.  It  is  mixed  with  clean 
asbestos,  which  occupies  the  same  position  in  the  tube  as  any  of 
the  other  absorbents. 

As  a  means  of  perfect  desiccation  it  is  often  required  to  com- 
bine the  absorbent  powers  of  two  different  materials  in  one  appa- 
ratus, and  for  this  purpose  the  U-form  of  drying-tube  is  most 
convenient.  It  presents  a  large  extent  of  surface  in  a  limited 
space.  There  is,  however,  a  disadvantage  in  arranging  and 
adjusting  its  parts  firmly  together,  and  also  in  the  necessity  of 
occasionally  renewing  the  hygroscopic  substance  more  frequently 
than  in  the  straight  tubes. 

Fig.  396  exhibits  a  proper  arrangement  of  the  U-tubes  for  the 

Fig.  396. 


desiccation  of  gas.     By  this  mode  the  gas  may  be  introduced 
directly  from  the  generating  vessel,  as  shown  at  Fig.  218,  or  from 


PRECIPITATION.  491 

a  gas  bag  or  gasometer  as  seen  in  the  preceding  drawing.  The 
latter  communicates  with  a  pair  of  U-shaped  glass  tubes,  which 
are  connected  together  by  means  of  bent  tubes,  perforated  corks, 
and  flexible  india-rubber  joints.  In  one  of  their  legs  is  placed 
dried  chloride  of  calcium,  and  in  the  opposite  one  asbestos,  or 
lumps  of  pumice-stone,  impregnated  with  sulphuric  acid.  The 
reservoir  on  the  top  of  the  gasometer  being  filled  with  water,  and 
its  pressure  applied  by  opening  the  cocks,  a  stream  of  gas  is 
gradually  expelled,  and  in  its  transit  through  the  tubes  is  freed 
from  its  moisture  by  the  absorbents. 


CHAPTER   XXV. 

PRECIPITATION. 

THIS  process  is  employed  for  the  immediate  separation  of  a 
body  in  the  solid  state,  both  from  mechanico-chemical  and  simple 
solutions.  The  reagent,  which  is  used  to  produce  the  action,  is 
termed  the  precipitant,  and  the  resulting  deposit  the  precipitate. 

Bodies,  in  some  instances,  may  be  precipitated  unaltered,  but 
in  most  cases,  being  the  result  of  chemical  reaction,  are  modified 
or  entirely  changed  in  their  nature.  Thus,  for  example,  sulphate 
of  lime  may  be  precipitated  from  its  simple  aqueous  solution  by 
alcohol ; — this  latter,  by  union  with  the  water,  forming  a  liquid 
in  which  that  salt  is  insoluble.  For  like  reasons,  the  resins  are 
precipitated  from  alcoholic  solutions  by  water ;  and  gutta-percha 
from  solution  in  chloroform  by  ether.  If,  however,  carbonate 
of  soda  or  other  soluble  carbonate  is  substituted  for  the  alcohol, 
in  the  instance  of  sulphate  of  lime,  then  the  original  combina- 
tion is  broken  up  by  the  action  of  double  elective  affinity,  an 
exchange  of  bases  taking  place,  and  insoluble  carbonate  of  lime 
precipitating  instead  of  the  unaltered  sulphate,  as  in  the  instance 
with  alcohol.  So,  also,  an  analogous  result  would  ensue  by  virtue 
of  simple  elective  affinity  if  soda  is  used  instead  of  the  carbonate, 
the  lime  then  partially  falling  in  a  free  state,  having  been  de- 
prived of  its  sulphuric  acid  by  the  caustic  alkali. 

The  consistence  of  the  precipitate  and  its  form  and  color  vary 
with  the  nature  of  the  solutions,  and  the  rapidity  with  which  it 


492  PRECIPITATION. 

is  produced.  These  distinctive  features  serve  as  characteristics 
by  which,  in  analysis,  the  presence  of  certain  bodies  is  deter- 
mined. 

The  precipitate  is  differently  termed  according  to  its  appear- 
ance.    It  is  flocculent  when  it  falls  in  small  flakes  or  flocculse, 
like  those  produced  by  ammonia  in  solutions  of  peroxide  of  iron ; 
pulverulent,  when  in  fine  powder  and  compact,  like  the  sulphates 
of  lead  or  of  baryta ;  granular,  if  deposited  in  minute  irregular 
molecules ;  crystalline,  when  it  subsides  in  minute  crystals,  as  the 
bitartrate  of  potassa,  sulphates  of  silver  and  of  lime  ;  curdy,  when 
cheesy,  like  that  thrown  down  by  chloride  of  sodium  from  nitrate 
of  silver,  and  gelatinous,  when  of  the  consistence  of  jelly,  as 
alumina  freshly  separated  from  alum  by  carbonate  of  potassa. 
Precipitating  Vessels. — The  most  convenient  vessels,  used  in 
analysis,  are  beaker  glasses,  or  wide-mouth 
Fig.  397.  flasks,  the  latter  being  used  only  when  the 

process  is  to  be  practised  upon   the  boiling 
liquid.      When    solutions    are    precipitated, 
especially  for  the  purpose  of  collecting  the 
precipitates,  the  form  of  the  vessel  may  be 
that  of  the  one   in  the  drawing,  Fig.  397, 
which  insures  the  subsidence  of  all  the  deposit, 
and  prevents  particles  from  adhering  to  the 
sides.     They  may  be  of  glass  or  blue  stoneware,  according  to 
the  amount  of  liquid  under  process. 

In  chemical  investigations,  test-tubes  are  the  most  convenient 
implements.  They  permit  the  operator  to  use  minute  quantities, 
and  they  are  readily  heated  and  shaken.  As  a  precipitate  is,  in 
some  instances,  not  perceptible  for  some  hours,  especially  in  dilute 
solutions,  sufficient  time  should  be  allowed  to  elapse  before  de- 
ciding upon  the  reaction  of  a  precipitant  upon  a  solution. 

Directions  for  Precipitating. — Both  the  material  and  reagent 
must  be  in  solution  and  separately  clarified  by  filtration  before 
being  commingled,  otherwise  the  suspended  matters  will  subside 
with  the  precipitate.  As  heat  generally  promotes  the  reaction 
and  the  subsidence  of  the  precipitate,  the  solution  should,  in  such 
cases,  be  warmed,  or  even  made  hot,  and  the  reagent  cautiously 
added  during  continual  stirring  with  a  glass  rod,  so  that  all  parts 
of  the  liquid  may  be  brought  in  contact.  The  vessel  is  then  set 


DECANTATION — FILTRATION.  493 

aside  upon  a  sand-bath,  or  in  a  warm  place,  until  the  deposition 
of  the  precipitate  has  left  the  supernatant  liquor  clear.  A  few 
more  drops  of  precipitant  are  then  added,  and,  if  all  the  matter 
has  been  thrown  down,  they  will  produce  neither  precipitate  nor 
cloudiness ;  but  if  a  portion  still  remains  in  solution,  still  more  of 
the  reagent  must  be  added.  The  addition  of  the  reagent  or  pre- 
cipitant must  be  gradual,  for  besides  the  waste  of  material  and 
inconvenience  of  washing  it  out,  an  excess,  in  certain  instances, 
redissolves  the  precipitate.  As  soon  as  a  drop  or  two  of  reagent 
ceases  to  give  cloudiness  or  precipitate  in  its  descent  through  the 
supernatant  liquid  of  the  settled  solution,  its  addition  must  be 
discontinued  and  the  vessel  placed  aside,  and,  after  sufficient 
repose,  subjected  to  DECANTATION  or  FILTRATION  to  separate  the 
solid  from  the  liquid  portion,  the  latter  of  which  is  also  usually 
to  be  reserved  in  analysis  or  when  it  is  of  value,  as  it  may  con- 
tain other  newly-formed  compounds  dissolved  in  the  menstruum 
employed. 

When  the  precipitate  about  to  be  formed  is  somewhat  soluble 
in  the  liquid  of  the  original  solution,  the  amount  of  that  liquid 
must  be  diminished  by  evaporation,  and  the  precipitation  effected 
in  a  concentrated  solution  ;  for  example,  in  the  reaction  of  solu- 
tions of  strontia  with  sulphuric  acid  or  soluble  sulphates. 

Metals  may  be  precipitated  from  their  solution  by  other  metals 
having  a  greater  affinity  for  oxygen  than  is  possessed  by  those  in 
combination ;  thus  copper  may  be  precipitated  from  its  sulphate 
by  iron,  lead  from  the  nitrate  by  zinc,  and  silver,  arsenic,  and 
mercury,  from  their  solutions  by  copper.  A  slight  acidulation 
of  the  liquid  facilitates  the  process,  and  the  metallic  strips  used 
as  reagents  must  be  clean  and  bright. 

Metals  are  also  precipitated  by  voltaic  action,  a  familiar  in- 
stance of  which  is  the  art  of  plating  by  GALVANISM. 


CHAPTER  XXVI. 

DECANTATION— FILTRATION. 

Precipitates,  which  are  substances  deposited  by  any  means 
from  liquids  in  which  they  have  been  dissolved  or  chemically 


494      .  POURING. 

combined,  may  be  separated  either  by  decantation  or  filtration. 
The  first  mode  is  applicable  to  those  solids  which  are  of  much 
greater  density  than  the  menstrua  containing  them,  and  which 
readily  and  rapidly  subside,  forming  heavy  compact  deposits.  In 
delicate  experiments,  however,  and  in  all  cases  where  the  liquid 
is  turbid  and  deposits  its  suspended  matter  reluctantly,  the  latter 
plan  is  the  most  appropriate. 

Besides  being  a  process  subsequent  to  PRECIPITATION,  for  the 
separation  of  the  clear  supernatant  liquor  from  the  subsident 
matter,  decantation  is  also  useful  in  LEVIGATION.  For  WASHING 
precipitates,  which  require  a  large  amount  of  water,  or  frequent 
renewals  of  the  wash  waters,  it  is  much  more  convenient  than 
filtration.  This  latter  mode,  however,  must,  as  before  said,  be 
always  adhered  to  in  analyses,  and  when  the  precipitate  is  light 
and  apt  to  be  disturbed  during  decantation. 

Decantation  from  small  vessels  in  nice  experiments  is  practised 
by  gently  inclining  the  vessel,  whether  it  be  a  capsule,  as  at  Fig. 
398,  or  a  beaker  glass,  Fig.  399,  and  allowing  the  liquid  to  run 

Fig.  398.  Fig.  399. 


down  in  a  continuous  stream  along  a  glass  rod  placed  against  its 
rim  or  edge.  This  operation  of  pouring  requires  a  degree  of 
dexterity  which  is  indispensable  in  analytic  operations  in  order 
to  avoid  loss  of  material.  The  exact  position  of  the  rod  is  shown 
in  the  figures.  When  the  pouring  is  completed,  the  rod  should 
be  tilted  upwards  for  a  moment,  so  as  to  prevent  the  loss  of  ad- 
herent drops,  and  immediately  returned  to  the  vessel,  the  edge 
of  which  should  be  slightly  greased  so  as  to  effectually  prevent 
any  particle  of  liquid  from  passing  over.  These  precautions  are 
only  necessary  in  the  decantation  and  filtration  of  liquids,  during 
analytic  processes ;  so  much  care  being  unnecessary  in  less  im- 


Fig.  400. 


SYPHONS.  495 

portant  manipulations,  as  it  is  of  little  consequence  if  the  liquid 
does  carry  over  a  little  of  the  precipitate  or  suffers  a  slight  loss. 
If  the  bulk  of  liquid  is  very  small,  it  may  be  removed  with 
pipettes,  Figs.  106, 109,  p.  199;  for  larger  quantities  a  syphon  is 
requisite.  This  implement  may  be  of  glass  or  lead  tubes,  the 
former  being  cleanly  and  of  more  general  application  than  the 
latter.  The  shapes  given  in  the  drawings  refer  to  those  of  either 
material, 

Syphons. — The  most  simple  form  of  syphon,  Fig.  400,  is 
similar  to  an  inverted  V,  with  its  opposite 
branches  of  unequal  length.  The  long  leg 
may  be  from  12  to  20  inches  in  length,  the 
shorter  one  proportionably  less.  The  clear 
diameter  is  from  an  eighth  to  a  half  inch, 
according  to  the  extent  of  the  operation. 

This  syphon  is  inserted  and  filled  with 
water  or  any  other  liquid  which  is  without 
action  upon  that  in  the  vessel ;  the  mouth  of 
the  longer  leg  is  then  closed  with  the  finger, 
and  the  shorter  branch  introduced,  mouth 
downwards,  into  the  liquid  to  be  decanted, 
until  it  nearly  reaches  to  the  level  of  the  pre- 
cipitate without  disturbing  it.  Upon  remov- 
ing the  finger,  the  liquid  runs  out  in  a  con- 
tinuous stream,  and  may  be  almost  wholly  drawn  off  by  slightly 
inclining  the  vessel. 

The  rationale  of  the  operation  is  as  follows : — When  the  short 
leg  of  the  syphon  is  dipped  into  water  the  liquid  mounts  into  the 
tube  as  high  as  the  surface  of  that  which  is  in  the  containing 
vessel.  Now,  the  weight  of  the  atmosphere  bears  equally  upon 
the  surface  of  that  in  the  vessel  and  in  the  syphon,  but  if  the 
elastic  force  of  the  internal  air  is  removed  or  diminished  by  suc- 
tion with  the  mouth  at  the  other  end,  or  by  having  previously 
filled  the  syphon  with  water,  the  liquid  runs  over,  and  as  the 
weight  of  the  column  of  water  in  the  long  leg  is  greater  than 
that  in  the  short  one,  the  flow  will  be  continuous  while  the  mouth 
of  the  short  leg  is  immersed  in  liquid,  for  no  air  can  enter  to  pro- 
duce an  interruption. 

If  the  liquid  is  not  injurious  or  unpleasant  to  the  taste,  the 


496 


SYPHONS. 


Fig.  401. 


syphon  may  be  inserted  in  the  liquid  without  previous  filling, — 
suction  with  the  mouth  at  the  long  end  drawing  it  over. 

For  the  decantation  of  caustic  liquids  the  syphon  is  furnished 
with  a  lateral  tube,  as  shown  in  Fig.  401, 
which  serves  as  a  protection  to  the  mouth. 
Its  application  is  similar  to  that  of  the  one 
described  above  (p.  495) ;  the  short  leg 
is  dipped  into  the  liquid  to  be  decanted, 
the  lower  end  closed  with  the  finger,  and 
suction  practised  at  the  orifice  of  the  sup- 
plementary tube  until  the  air  is  removed 
and  the  liquid  runs  over  and  almost  reaches 
the  mouth,  when  the  decantation  goes  on 
continuously  after  the  withdrawal  of  the 
mouth  and  finger. 

The  annexed  drawing,  Fig.  402,  exhibits 
these  syphons  in  operation. 

A  length  of  cotton  wick  doubled  in 
syphon  form,  and  having  its  short  end  immersed  in  the  liquid, 
also  acts  as  a  syphon,  but  is  much  slower  in  its  operation. 


Fig.  402. 


s— Q 


Fig.  403. 


Coffee's  syphon,  Figs.  403,  404,  which  may  be  made  of  either 
glass  or  metal,  after  the  forms  presented  by  the  drawings,  are 
much  more  convenient  than  either  of  the  preceding  patterns,  as 
they  deliver  the  clear  liquid  without  the  least  inconvenience  to 
the  operator. 


SYPHONS. 


497 


It  is  made  to  work  by  closing  the  cock,  compressing  the  india- 
rubber  ball,  which  forms  a  cap  to  the  lateral  tube,  and  quickly 
immersing  the  short  leg  in  the  liquid  to  be  drawn  off.  The  hand 
being  removed  from  the  ball  causes  the  latter  to  resume  its  shape, 
and,  consequently,  a  partial  vacuum  in  the  tube,  which  is  imme- 

Fig.  404. 


diately  supplied  by  the  liquid  running  up  to  fill  it,  under  the 
outward  pressure  of  the  air,  as  far  as  the  bend,  and  therefore 
when  the  cock  is  opened,  it  drops  by  the  force  of  gravitation,  and 
flows  off  in  a  continuous  stream,  as  long  as  the  mouth  of  the  short 
leg  is  covered  by  it. 

The  use  of  the  syphon  allows  the  separation  of  the  liquid  with- 
out disturbance  of  the  settled  matter,  but  as  the  latter  still  retains 
more  or  less  fluid  which  cannot  be  separated  in  this  way,  it  may 
be  thrown  upon  a  filter,  and,  in  large  operations,  even  subjected 
to  pressure  in  cloths,  as  directed  at  p.  460. 

FILTRATION. — The  mode  most  commonly  resorted  to,  for  sepa- 
rating solid  substances  from  liquids  in  which  they  are  suspended, 
is  that  of  filtration,  and  it  is  also  occasionally  but  rarely  used 
for  the  purpose  of  disuniting  liquids.  The  process  consists  in 
passing  the  mixture  through  suitable  media  of  sufficient  porosity 
to  allow  the  transit  of  the  liquid  portions  while  they  intercept 

32 


498  FILTRATION  THROUGH   PAPER. 

any  solid  particles.  For  the  separation  of  liquids  the  texture  of 
the  medium  must  be  such  that  it  is  penetrable  by  or  attractive  of 
the  one,  but  impervious  to  the  other,  of  them,  as  it  is  upon  this 
that  the  success  of  the  operation  depends ;  thus,  for  example, 
moistened  paper  will  allow  the  passage  of  water,  but  not  of  oil. 

Paper,  brown  muslin,  linen,  crash,  woollen  and  canton  flannel, 
felt,  raw  cotton,  sand,  asbestos,  crushed  quartz,  bone-black,  each 
and  all  have  their  appropriate  application  as  media,  and  when 
thus  used  are  all  styled  filters  or  strainers ;  the  first  title  being 
almost  exclusively  applied  to  those  of  paper  supported  upon 
funnels,  while  the  latter  is  limited  to  the  other  textures  or  bodies 
which  are  either  suspended  upon  frames  for  pharmaceutical  ope- 
rations or  deposited  in  proper  vessels. 

This  process  is  of  equal  importance  in  chemical  and  pharma- 
ceutical operations.  In  analysis  it  enables  us  to  separate  preci- 
pitates or  insoluble  residue  from  liquids,  and  to  obtain  each  free 
from  particles  of  the  other, — an  indispensable  condition  where 
both  are  to  be  further  acted  upon  for  obtaining  accurate  results; 
while,  in  ordinary  operations,  we  can  by  its  aid  free  liquids  from 
dirt  and  other  foreign  matters,  and  render  them  transparent. 

FILTRATION  THROUGH  PAPER. — Paper  is  more  generally  used, 
particularly  in  delicate  experiments,  than  any  other  medium.  It 
is  advisable  always  to  use  that  which  is  white,1  for  it  contains  no 
coloring  matter  to  deteriorate  the  liquid  which  traverses  it. 
Moreover,  it  should  be  free  from  saline  impurities  which  are 
soluble  in  acid  or  alkaline  liquids,  otherwise  the  accuracy  of 
analytic  results  may  be  materially  interfered  with. 

The  laboratory  should  be  provided  with  two  qualities  of  paper, 
one  of  fine  quality  for  nice  investigations,  and  another  somewhat 
inferior  for  the  less  important  processes.  There  are  certain 
conditions  requisite  in  both  kinds.  They  should  be  unsized, 
yet  strong,  and  while  sufficiently  porous  to  allow  the  ready  pas- 
sage of  the  liquid,  compact  enough  in  texture  to  retain  all  the 
solid  portions'. 

"  German  filtering  paper"  answers  very  well  for  all  general 
purposes ;  but  for  analytic  investigations  that  known  as  "  Swe- 

1  A  porous  kind  of  thick  brown  paper  is  made  from  a  mixture  of  woollen  and 
other  rags  for  filtering  tinctures  and  the  coarser  liquids  of  an  aqueous  or  spirituous 


nature. 


FILTRATION  THROUGH   PAPER. 


499 


d  sh  fUenng  paper  „  best.  Being  made  expressly  for  the  pur- 
pose  and  of  purified  rags,  it  is  free  from  lime,  copper,  and  salts, 
winch  have  to  be  removed  from  other  paper  by  treatment  with 
pure  hydrochloric  acid  and  repeated  rinsings  in  distilled  water 
before  it  becomes  fit  for  such  uses. 

The  Swedish  paper  is  whiter  and  thinner  than  the  German 
and  is  made  with  great  care;  and  leaves  by  incineration  only 
*****  of  its  weight  of  ashes,  an  important  point  in  analyses  where 
the  amount  and  nature  of  the  ashes  left  by  the  paper  require  to 
be  considered. 

The  paper  drawer  should  be  kept  always  supplied  with  a  stock 
of  filters  of  all  the  required  sizes.  The  use  of  the  Swedish  paper 
should  be  limited  to  the  filtration  of  finely  divided  precipitates. 
The  greater  porosity  of  the  German  renders  it  more  applicable 
for  rapid  filtration,  and  as  it  is  much  less  expensive,  all  large 
filters  should  be  formed  of  it. 

The  filters  must  be  circular,  and  cut  by  tin  patterns,  which 
should  consist  of  different  sizes  of  2J,  3,  3},  4J,  6,  7J,  9,  and 
12  inches  in  diameter.  This  mode  of  cutting  different  sized  filters 
from  one  sheet  of  paper  is  economical,  and  saves  the  waste  which 
would  be  occasioned  by  indiscriminate  use  of  the  paper,  while 
many  serious  delays  may  be  prevented  by  having  a  supply  always 
at  hand. 

The  ashes  of  the  piece  of  Swedish  filter  of  each  size  must  be 
determined  by  incinerating  one  and  accurately  weighing  the  resi- 
due, and  engraving  its  weight  upon  the  tin  pattern  by  which  it 
is  formed.  Thus,  in  analyses,  we  can  know  by  reference  to  the 
figures  the  amount  of  fixed  matter  (ash)  in  each  particular  size. 

The  supports  for  these  circular  filters,  folded  into  conical  form 
as  hereafter  directed,  are  funnels,  which  vary  in  material  and 
form  according  to  the  nature  of  the  operation.  They  may  be 
of  glass,  porcelain,  or  stoneware.  The  first,  free  from  lead,  are 
of  almost  general  application  for  analytic  purposes,  and  the  latter 
two  for  pharmaceutical.  Funnels  of  metal  are  seldom  required 
in  the  laboratory,  a  very  few  instances  only  demanding  the  use 
of  lead  or  platinum. 

The  glass  funnels  should  be  made  with  straight  sides,  inclining 
to  an  angle  of  about  60°.  This  shape,  Fig.  405,  is  indispensable 
for  the  smaller  funnels  used  in  analyses,  as  it  forms  in  its  inte- 


500  FUNNELS. 

rior  a  true  cone,  which  allows  the  admission  of  a  larger  amount 
of  liquid  in  a  small  space.     The  pint  funnels,  and  those  of  still 
larger  size,  may  have  an  inclination  of  ten 
Fig-405-  degrees  less,  but  if  their  section  has  not 

nearly  the  form  of  an  equilateral  triangle, 
the  filters  fit  badly  and  work  imperfectly. 
The  funnel  should  be  slightly  round  at  the 
shoulder  a,  where  the  apex  of  the  conical 
filter  rests ;  and,  moreover,  the  end  of  the 
barrel  c  ought  to  be  cut  at  an  angle  of  30°, 
so  as  to  present  an  oblique  termination,  as 
these  points  promote  filtration. 

The  laboratory  must  be  supplied  with  a 

series  of  funnels,  ranging  as  follows,  1£,  1},  2,  2J,  3J,  4J,  5J,  and 
6J  inches  in  the  greatest  diameter  of  the  body  5.  Of  the  smaller 
sizes,  it  will  be  well  to  have  duplicates  or  triplicates  as  they  are 
the  most  frequently  employed.  The  stock  is  not  complete  with- 
out one  or  two  miniature  funnels  of  thin  glass  for  filtering  into 
test-tubes  in  qualitative  investigations ;  and  one  or  two  of  con- 
venient size  with  long  barrels  c,  for  charging  retorts  and  deep 
vessels. 

Sometimes  the  glass  funnels  are  ground  at  the  rim,  so  as  to  be 
tightly  closed  by  a  glass  disk,  but  being  ex- 
Fig.  406.  pensive,  they  are  only  used  in  rare  instances. 
Funnels  are  sometimes  made  of  porcelain 
with  longitudinal  ribs  in  the  interior  of  the 
body,  as  shown  at  Fig.  406,  for  preventing 
the  adhesion  of  the  filter  to  the  sides  in  the 
filtration  of  large  quantities  of  bulky  precipi- 
tates.    The  object  is,  however,  not  effected 
by  th-ese  means,  for  the  paper  sinks  into  the 
channels  and  adheres  to  the  surface,  and  still 
retards  the  passage  of  the  liquid.     A  better  way  will  be  to  use 
the  plaited  filters,  Fig.  416. 

Funnels  are  also  made  of  porcelain,  and  more  seldom  of  stone- 
ware. They  are  less  fragile,  and  more  applicable  to  the  filtration 
of  very  acid  and  corrosive  liquids,  and  some  other  few  purposes, 
than  those  of  glass ;  but  those  of  porcelain  are  not  less  costly. 
The  form  of  those  usually  found  in  the  market  are  shown  in  the 


FUNNELS. 


501 


annexed  drawing.  They  are  all  glazed  throughout  and  made 
very  strong,  and  those  used  for  transferring  liquids  from  one 
vessel  to  another  have  the  convenience  of  handles.  In  this 
respect  they  are  preferable  to  the  glass  vessels,  which  by  fre- 
quent rough  handling  are  more  apt  to  be  broken.  Fig.  407  ex- 
hibits the  form  used  for  acids,  and  Fig.  408  the  same  funnel 
ribbed  in  its  interior.  Figs.  409  and  410  present  the  less  conve< 


Fig.  407. 


Fig.  408. 


Fig.  409. 


nient  globular  shape.  Those  shown  at  Figs.  411  and  412,  cul- 
lendered  at  the  base,  are  the  most  convenient  of  all,  being  very 
useful  for  draining  crystals,  for  the  filtration  of  viscous  solutions 
through  cloth  filters,  and  for  small  operations  of  lixiviation. 

Separating  Funnels.— In  addition  to  the  above  there  are  two 
other  kinds  of  funnels  used  for  separating  liquids  which  have  no 


Fig.  413. 


Fig.  414. 


chemical  affinity,  and  differ  in 

stop-cocks  in  their  barrels,  as  shown  in  F.gs.  413  and  414;  and 


502 


FILTERS   FOLDED   AND  INTRODUCED   IN  FUNNELS. 


one  is  stoppered  also  at  the  top  to  prevent  evaporation  when  vola- 
tile liquids  are  under  process. 

The  mixed  liquids  of  oil  and  water,  or  ether  and  water,  for  in- 
stance, are  poured  in  the  mouth,  and  after  sufficient  repose  for 
the  deposition  of  the  heavier  of  the  two,  it  can  be  drawn  off  by 
opening  the  stop-cock,  which  may  be  immediately  closed  as  soon 
as  all  has  passed.  The  lighter  liquid  which  is  thus  retained  may 
afterwards  be  transferred  in  the  same  way  to  another  bottle. 

Filters  Folded  and  introduced  into  Funnels. — Two  kinds  of 
filters  are  generally  employed,  the  plain,  Fig.  415,  and  the  plaited, 
Fig.  416.  The  former  are  used  in  analyses  and  whenever  the 


Fig.  415. 


Fig.  416. 


suspended  or  precipitated  matters  of  a  liquid  are  to  be  preserved. 
It  is  almost  impossible  to  entirely  remove  the  solid  matter  from 
the  folds  of  a  plaited  filter,  consequently  such  are  chiefly  appli- 
cable for  the  filtration  of  bulky  precipitates  from  large  quantities 
of  liquid.  This  mode  of  folding  a  filter  prevents  its  close  adhe- 
sion to  the  glass,  and  greatly  expedites  the  process  by  increasing 
the  surface,  and  by  allowing  a  bubble  of  air  to  ascend  in  the  fold 
every  time  that  a  drop  of  liquid  descends  from  the  filter. 

The  plain  filters  are  folded  as  follows : — 

"  When  a  filtration  is  to  be  performed,  one  of  these  circular 


Fig.  418. 


papers  of  the  proper  size  is  selected  (Fig.  417),  and  then  doubled 


PLAIN  AND   PLAITED   FUNNELS. 


503 


over  one  of  its  diameters  (a  b,  Figs.  41T  and  418),  and  then  over 
the  radius  (e  e,  Figs.  418  and  419)  perpendicular  to  the  first  dia- 
meter, so  as  to  form  a  quadrant.  One  of  the  folds  is  then  opened, 

Fig.  419.        Fig.  420.  Fig.  481. 


' 


forming  a  hollow  cone,  as  represented  in  Fig.  421,  which  will  fit 
accurately  in  the  funnel,  if  the  sides  of  the  latter  form  an  angle 
of  60°.  If  the  angle  be  greater  or  smaller,  it  is  necessary  to 
double  the  filter  the  second  time  over  another  radius  (<?/,  Figs. 
417  and  420),  not  perpendicular  to  the  first  diameter,  and  then 
open  the  large  or  small  fold  (a  cf9orbcf9  Fig.  420)  according 
to  the  angle  of  the  funnel,  and  this  repeated  until  a  coincidence 
of  the  filter  with  the  inside  of  the  funnel  is  effected." 


To  form  the  plaited  filter,  take  a  square  of  paper  and  fold  it 
diagonally,  as  in  Fig.  422 ;  turn  A  upon  B  to  obtain  the  crease  E, 
and  open  it ;  then  double  A  upon  E  in  the  same  direction,  to  make 
the  plait  F,  and  double  the  plait  A  back  upon  F,  so  as  to  form  the 
crease  G,  and  holding  this  plait  between  the  fingers  make  the  fold 
between  F  and  D.  Divide  the  spaces  between  E  B  and  B  D  in  the 
same  manner. 

The  filters,  as  above  made,  after  having  their  folds  opened,  as 
at  Figs.  415  and  416,  are  placed  in  the  funnels,  and  so  adjusted 
as  to  fit  nicely  to  the  sides.  In  order  to  secure  an  uninterrupted 
flow  of  the  liquid,  and  to  prevent  the  breaking  of  the  filter,  the 
apex  must  not  extend  too  far  into  the  barrel  of  the  funnel. 
Moreover,  the  filter  should  be  a  little  smaller  than  the  funnel,  for 


504 


SUPPORTS   FOR   FUNNELS. 


if  it  reaches  to  the  rim,  evaporation  of  the  liquid  ensues  from  the 
edges,  and  thus,  in  analyses,  may  be  a  source  of  error. 

The  proper  position  of  the  plain  filter  in  the  funnel  is  shown  at 
Fig.  424,  and  that  of  a  plaited  one  at  Fig.  423. 

In  using  large  funnels  the  filter  maybe  supported  by  a  plug 
of  raw  cotton  placed  in  the  barrel  at  its  junction  with  the  body. 


Fig.  423. 


Fig.  424. 


The  usual  support  for  funnels  is  the  convenient  portable  stand, 
Fig.  424.  It  consists  of  a  wooden  upright  £>,  screwed  into  a 
wooden  bed-plate.  The  arm  a,  which  it  carries,  has  a  circular 
aperture  sloping  inwardly  and  downwards,  which  supports  the 
funnel  steadily  in  its  place.  The  screw  c  allows  the  elevation  or 
depression  of  this  arm  at  will,  as  the  height  of  the  receiving- 
vessel  beneath  may  require. 

When  the  funnel  is  used  for  transferring  or  filtering  liquids 
into  narrow-mouthed  vessels,  its  barrel  may  be  supported  by 
their  neck ;  but  in  order  to  secure  a  free  passage  of  air,  it  should 
be  fluted  externally,  or  else  have  a  chip  or  two  placed  between  it 
and  the  inner  sides  of  the  neck,  otherwise  the  confined  air  will 
retard  the  process,  and  possibly  force  the  filtered  liquid,  with  a 
hissing  sound,  up  and  over  the  sides  and  mouth  of  the  bottle. 

After  having  adjusted  the  filter  to  the  funnel,  the  latter  is 
placed  in  the  stand,  so  that  its  barrel  may  rest  against  the  inner 
wall  of  the  receiving-vessel  beneath.  This  position  allows  the 
falling  fluid  to  trickle  quietly  down  the  sides,  and  prevents  the 


SUPPORTS  FOR  FUNNELS.  505 

splashing  which  would  occur  if  it  fell  directly  upon  the  surface  of 
the  liquid,  and  also  obviates  the  necessity  of  sinking  the  harrel 
far  into  the  receiver. 

The  filtering  apparatus  having  been  thus  arranged,  the  filter 
is  to  be  moistened  with  distilled  water  from  the  bottle  (Fig.  355) 
or  when  the  nature  of  the  process  requires,  with  a  portion  of  the 
solvent  liquid,  and  the  excess  allowed  to  trickle  through,  rather 
than  be  emptied  out  by  inverting  the  funnel.  This  previous 
soaking  of  the  filter  greatly  facilitates  the  operation,  for  dry 
paper  absorbs  water  directly,  and  in  the  case  of  a  turbid  solution, 
while  becoming  more  impervious  to  the  suspended  particles  than 
it  would  be  if  the  liquid  which  contains  them  were  allowed  to 
penetrate  at  once  into  the  filter,  it  gives  also  a  more  ready  pas- 
sage to  the  clear  fluid.  The  edges  of  the  containing  vessel  are 
now  to  be  slightly  greased  in  one  spot,  so  that  in  pouring  there 
may  be  no  adhesion  of  drops  or  trickling  over  the  sides.  It  is 
then  grasped  by  the  right  hand  and  brought  over  the  funnel, 
while  the  left  hand  holds  the  glass  rod  at  a  right  angle  against 
the  edge  of  the  glass,  as  shown  at  Fig.  425.  The  end  of  this  rod 

Fig.  425. 


should  merely  reach  the  filter  without  touching  it,  for  fear  of 
abrasion  ;  and  the  liquid  should  be  allowed  to  flow  down  its  length 
in  a  gentle  stream  at  first  against  the  sides,  and  as  the  precipi- 
tate accumulates  it  may  be  allowed  to  fall  in  the  centre,  as  there 
is  then  less  risk  of  splashing.  The  filter  should  never  be  entirely 
filled,  and  as  it  often  requires  many  pourings  to  pass  the  whole 
of  the  liquid,  great  care  must  be  taken  in  returning  the  rod  t 
vessel  that  nothing  be  lost.  The  last  particles  maybe  rinsed 
from  the  vessel  and  rod  by  the  jet  of  the  spritz  bottle  A 


506 


THE   SPRITZ. 


426),  by  inclining  both  to  the  positions  shown  in  the  drawing 
below.     If  any  remaining  particles  still  obstinately  adhere  to  the 

Fig.  426.  . 


sides  of  the  glass,  or  of  the  rod,  they  must  be  loosened  by  the 
feather  end  of  a  goosequill,  and  then  washed  out  as  before  by 
the  jet  of  the  spritz.  When  all  the  liquid  has  passed  through,  the 
precipitate  must  be  washed  down  from  the  sides  of  the  filter  by 
the  force  of  the  jet  of  water  from  the  spritz. 

The  spritz,  or  washing-bottle,  consists  of  a  twelve  ounce  vial, 

Fig  427. 


to  the  mouth  of  which  is  adapted,  by  means  of  a  perforated  cork, 
a  glass  tube,  drawn  out  at  its  upper  end  as  shown  in  Fig.  427, 
Fig.  428.  which  represents  at  the  same 

time  its  exact  dimensions.  The 
bottle  is  rather  more  than  half 
filled  with  water,  and  by  blow- 
ing into  it  through  the  tube  the 
air  is  compressed,  and  when  the 
bottle  is  quickly  inverted  it 
forces  out  the  water  through 
the  orifice  in  a  strong  jet,  which 
may  be  directed  to  any  desired 
point.  The  bottle,  complete,  is 
exhibited  at  Fig.  428.  For 
washing  out  beaker  glasses,  or  other  deep  vessels,  a  curved  jet 


WASHING   BOTTLES.  597 

is  more  convenient,  and  is  seen  at  A,  Fig.  426.  An  india-rubber 
ball  may  replace  the  bottle,  it  being  only  necessary  to  fit  the 
tube  in  the  neck,  and  tighten  the  joint  with  a  twine  wrapping. 
This  instrument  is  managed  as  directed  for  the  pipette,  p.  200. 

When  hot  water  is  required,  the  bottle  should  be 
of  copper,  tinned  on  the  inside,  of  at  least  a  pint 
capacity,  and  of  the  form  presented  by  Fig.  429. 
It  is  heated  as  directed  at  p.  231,  Fig.  185,  and 
to  prevent  burning  of  the  hand,  is  fitted  with  a 
non-conducting  handle.  Upon  inversion  of  the 
bottle,  the  water  is  driven  through  the  tube  d  in 
a  strong  jet  by  the  elastic  force  of  the  confined 
vapor. 

In  dusty  apartments,  both  funnel  and  receiving-vessels  should 
be  kept  covered  by  circular  or  square  pieces  of  window-glass. 
The  one  over  the  receiver  should  have  an  opening  in  the  side  for 
the  passage  of  the  barrel  or  tube  of  the  funnel. 

The  receivers  are  most  generally  beaker  glasses,  but  capsules, 
flasks,  and  narrow-necked  bottles  are  all  made 
use  of.     The  above  precautions  refer  espe-  Fig.430. 

cially  to   filiations   in   analytic   operations.     CH^H^-^ 
In  larger  operations  the  manipulation  is  not,      \      / 
necessarily,  so  strict,  and  when  the  dimen- 
sions of  the  containing  vessel  will  not  admit  of  convenient  hand- 
ling, its  contents  may  be  conveyed  to  the  filter  by  ladlesful  in  the 
small  porcelain  dipper,  Fig.  430.     The  ladle,  during  the  inter- 
vals of  the  transfers,  must  rest  in  a  plate,  and  not  be  placed  any- 
where in  the  dust. 

In  order  to  expedite  the  process,  the  liquid,  as  a  general  rule, 
should  be  allowed  sufficient  repose  previous  to  filtration,  to  de- 
posit if  possible  all  its  suspended  matter,  and  the  clear  superna- 
tant portion  should  be  passed  through  first.  The  subsident 
matter  being  added  last,  is  filtered,  as  it  were,  alone,  and  offers 
no  impediment  by  obstructing  the  pores  of  the  filter  to  the 
passage  of  the  liquid  portion,  as  it  would  if  mixed  with  it.  As 
an  exception  to  this  rule,  certain  precipitates  which  are  curdy, 
gelatinous,  flocculent,  or  crystalline,  may  be  filtered  immediately 
after  their  formation.  As  warmth  usually  expedites  the  process, 
nearly  all  liquids,  when  circumstances  permit,  should  be  filtered 
whilst  hot. 


508 


FILTRATION   PROMOTED   BY  WARMTH. 


Below  is  a  drawing  of  an  apparatus,  Fig.  431,  convenient  for 
keeping  liquids  warm  during  the  operation,  and  known  as  Hare's 
filter-bath.  It  consists  of  an  oval  copper  jacket,  flat  at  top  and 
bottom,  with  two  conical  apertures  through  its  body.  The  cone, 
with  its  expanded  part  directed  downwards,  is  a  sort  of  chimney, 
under  which  a  spirit-lamp  is  placed  to  heat  the  water  in  the  bath, 
and  the  other  is  a  bed  for  the  funnel.  To  prevent  ignition  of  the 
vapors  when  inflammable  liquids  are  under  process,  there  is  a 
partition  beneath. 


Fig.  431. 


Fig.  432. 


This  apparatus  is  particularly  applicable  for  the  filtration  of 
oils  and  viscous  liquids.  For  small  operations,  such  as  ana- 
lytical experiments,  it  may  be  conveniently  replaced  by  a  very 
simple  arrangement,  suggested  by  Normandy.  It  consists  of  a 
common  glass  flask  two-thirds  full  of  water,  and  connected  by  a 
leaden  pipe  with  a  circular  dish,  having  a  rim  in  the  interior  for 
the  support  of  a  bell  glass  with  an  open  mouth.  The  beaker 
which  receives  the  filtrate  is  placed  upon  a  stand  in  the  centre 
of  the  dish,  and  above  it  is  the  paper  filter  supported  in  a  pla- 
tinum ring,  as  seen  in  the  drawing,  Fig.  432. 

Heat  being  applied  to  the  flask,  steam  is  soon  generated,  and, 
passing  into  the  bell,  eventually  escapes  through  the  mouth. 
The  filter  being  thus  constantly  surrounded  by  an  atmosphere  of 
hot  vapor,  not  only  delivers  its  filtrate  clear  and  rapidly,  but 
also  free  from  the  action  of  atmospheric  air. 


FILTRATION  THROUGH   CLOTHS.  509 

For  filiations  of  heavy  precipitates,  or  a  large  amount  of 
liquid,  it  is  advisable  to  u«e  the  filter  doubled,  or  even  trebled,  as 
it  will  be  thus  enabled  to  resist  a  very  heavy  weight.  This  pre- 
caution is  necessary  also  when  the  liquid  runs  through  a  single 
paper  turbid.  When  only  the  first  runnings  are  turbid,  a  single 
filter  will  answer  for  small  experiments,  but  the  liquid  must  be 
repassed  through  the  same  medium. 

FILTRATION  THROUGH  CLOTHS. — In  large  operations,  or  when 
the  solid  matter  to  be  separated  is  too  heavy,  or  would  corrode 
or  clog  the  pores  of  paper,  the  latter  is  replaced  by  cloth.  The 
kinds  of  cloth  vary,  and  each  of  those  already  mentioned  has  its 
appropriate  application.  The  texture  of  the  medium  must  be 
adapted  to  the  consistence  of  the  liquid ;  for  example,  flannel  or 
felt  may  be  used  for  filtering  mucilaginous,  saccharine,  and 
slightly  acidulous  solutions ;  twilled  cotton  or  canton  flannel  for 
oils ;  linen  and  muslin  for  tinctures,  vegetable  juices,  and  dilute 
alkaline  lyes.  Sieves  of  bolting  cloth  are  occasionally  used  for 
filtering  liquids  from  very  fine  or  flocculent  matters. 

Filters  made  of  the  materials  above-mentioned,  and  which  take 
the  name  of  strainers,  instead  of 
being  used  like  those  of  paper,  are  Flg  433< 

suspended  upon  square  frames 
formed  of  four  pieces  of  lath,  as 
shown  at  Fig.  433.  These  frames, 
of  which  there  should  be  several 
sizes,  must  be  strongly  jointed,  and 
should  have  inserted  upon  their 
upper  surfaces  a  number  of  rectan- 
tangular  hooks,  similar  to  those 

used  in  the  drying-lofts  of  calico  factories  for  hanging  up  the 
printed  goods.  The  cloth,  of  whatever  kind,  being  cut  into  a 
square  of  size  proportioned  to  that  of  the  frame,  is  stretched  over 
it  very  loosely,  and  retained  in  position  by  hitching  its  margin  on 
these  tacks  or  hooks.  This  mode  is  far  preferable  to  that  of 
nailing  the  cloth  down  with  flat-headed  tacks,  for  besides  the 
injury  of  material,  there  is  less  convenience  in  removing  it  if* 
the  filtration  for  pressure,  or  for  replacing  it  with  another  when 
it  is  required.  The  support  for  these  strainers  is  an  upright 


510 


FILTRATION  THROUGH  CLOTHS. 


stand,  Fig.  434,  the  interval  between  the  legs  of  which  is  suffi- 
cient to  allow  the  free  entrance  of  the  receiving-vessel. 

Fig.  434.  Fig.  435. 


Fig.  430. 


"  When  the  cloths  are  made  into  conical  bags,  as  is  very  often 
the  case,  and  not  without  advantage,  they  are  to  be  suspended 
by  loops  to  a  transverse  beam,  as  shown  in  Fig.  435.  The  loops 
or  hangers  are  fastened  to  the  ring,  Fig. 
436,  around  which  the  rim  of  the  bag  is 
hooked.  These  bags  allow  the  conve- 
nience of  using  narrow-mouthed  receivers, 
as  the  liquid  trickles  through  in  a  stream 
from  the  most  depending  parts. 

The  texture  of  the  straining-cloth  must 
be  porous,  but  sufficiently  compact  to 
prevent  the  passage  of  any  solid  par- 
ticles. It  is  far  more  convenient  than  paper  for  coarse  filtration 
of  decoctions,  tinctures,  oils,  syrups,  and  for  separating  liquids 
from  solid  organic  matters.  In  most  instances,  the  cloth  or  bag 
may  be  renovated  by  washing,  and  thus  be  rendered  fit  for  other 
operations. 

Before  stretching  the  cloth  upon  the  frame,  or  suspending  the 
bags,  they  should  be  first  moistened  with  water,  or,  if  necessary, 
with  a  portion  of  the  solvent  liquor,  in  order  to  swell  the  fibres 
and  contract  the  meshes.  The  liquid  should  be  then  introduced 
gradually  without  spilling.  For  this  purpose,  a  tinned,  copper, 
or  porcelain  ladle,  Fig.  437,  with  a  wooden  handle,  is  very  con- 


FILTRATION  THROUGH   PULVERULENT   MATTERS.  511 

venient.     A  very  excellent  substitute  is  a  dipper,  made  from,  a 
cocoa-nut  shell,  and  sold  in  any  of  the  furnishing  shops.     Addi- 

Fig.  437. 


tions  of  liquid  should  be  made  until  the  filter  is  nearly  full,  and 
it  should  be  kept  at  the  same  level  by  renewing  it  as  fast  as  it 
runs  through.  If  the  first  runnings  are  turbid,  they  should  be 
returned  to  the  filter,  and  if  they  continue  murky,  repassed 
through  a  fresh  cloth. 

After  all  the  liquid  has  passed  through  in  this  way,  the  cloth 
or  bag  is  to  be  unhooked,  carried  to  a  table,  securely  folded,  and 
enveloped  in  a  wrapper,  and  subjected  to  pressure  as  directed  at 
p.  459,  for  the  expulsion  of  the  retained  portion  of  liquid.  The 
precipitate  thus  pressed,  when  an  object  of  value,  is  to  be  cut  up 
with  a  spatula  and  spread  on  frames  for  DESICCATION. 

The  cloths  are  then  to  be  immediately  rinsed  and  cleaned  in 
water  without  soap,  dried,  and  placed  away  for  service  at  another 
time. 

FILTRATION  THROUGH  PULVERULENT  MATTER.  —  Crushed 
quartz,  clean  white  sand,  asbestos,  bone-black,  and  charcoal,  are 
the  materials  generally  used  as  media.  The  two  latter  act  both 
as  filtering  and  purifying  agents,  as  the  liquid  becomes  not  only 
clarified  in  its  passage,  but  freed  from  coloring  and  putrescent 
matters,  if  any  exist  in  it.  The  others  are  used  for  the  filtration 
of  very  acid  or  corrosive  liquids,  which  would  be  destructive  of 
paper  or  cloth,  and  partially  solvent  of  bone-black. 

All  of  these  substances  may  be  used  in  funnels,  a  thin  stratum 
being  placed  in  the  bottom  of  the  body,  and  prevented  from 
escaping  through  the  barrel  by  a  loose  cotton  plug  in  the  neck. 

A  funnel  plugged  in  this  manner,  even  without  the  stratum  of 
pulverulent  medium,  answers  an  excellent  purpose  for  the  filtra- 
tion of  liquids  which  pass  through  freely,  and  whose  suspended 
matter  is  in  coarse  particles. 

It  will  of  course  be  remembered  that  the  use  of  these  media  is 
only  practicable  when  the  liquid  is  the  sole  object  of  value,  for  it 
would  be  impossible  to  prevent  at  least  the  partial  admixture  of 
the  suspended  matter  with  the  secerning  agent. 

The  asbestos,  sand,  and  charcoal,  should  first  be  treated  with 


512 


FILTRATION   OF   VOLATILE   LIQUIDS. 


Fig.  438. 


muriatic  acid  to  remove  soluble  matters,  and  then  thoroughly 
rinsed  with  fresh  "water  to  remove  all  traces  of  acid  previous  to 
their  employment  as  filtering  means.  Freshly  prepared  and 
finely  powdered  charcoal,  by  its  absorbent  power,  deprives  most 
liquors  of  their  fetor  and  organic  coloring  matter  ;  bone-black  has 
the  same  effect,  but  in  a  much  less  degree.  These  two  are  the 
best  substances  for  separating  impurities  from  syrups  and  aqueous 
liquids. 

•  The  filtering  substance  should  always,  before  being  used,  be 
moistened  throughout,  as  in  displacement,  with  clean  fluid,  or,  as 
is  proper  in  many  cases,  with  the  pure  liquid  which  is  the  solvent 
of  the  various  substances  in  the  fluid  which  is  to  be  depurated. 
Thus  the  substance  in  the  funnel  may  be  made  to  imbibe  water 
before  the  filtration  through  it  of  a  syrup,  and  alcohol  or  ether 
before  the  passage  of  tinctures  or  ethereal  solutions. 

Filtration  by  DISPLACEMENT,  to  which  the  above  mode  is  in 
some  respects  similar,  has  already  been  fully  described  at  p.  452. 
FILTRATION  OF  VOLATILE  LIQUIDS. — Donovan  has  contrived 
an  apparatus  for  filtering  liquids  which 
are  vaporizable  or  alterable  by  exposure 
to  air.     It  is  identical  in  principle  and 
construction  with  the  displacer,  Fig.  372, 
and  is  very  useful  for  filtering  alcoholic, 
ethereal,  or  ammoniacal,  and  alterable 
caustic  liquids. 

The  modification  of  Riouffe  is  more 
convenient  than  the  original  apparatus, 
as  it  allows  the  use  of  an  ordinary  funnel 
with  a  cover.  It  is  represented  by  Fig. 
438,  and  consists  of  a  glass  bottle  A,  with 
two  necks,  into  one  of  which  enters  the 
barrel  of  the  funnel.  The  neck  of  this 
funnel  is  loosely  closed  with  a  plug  of 
raw  cotton,  and  the  liquid  is  introduced 
through  the  s  tube  without  uncovering  or 
disturbing  the  apparatus,  As  the  liquid 
filters  through,  the  column  of  air  displaced  finds  a  vent  through 
the  narrow  tube  a,  adjusted  in  position  by  means  of  perforated 
corks.  The  stop-cock  K  allows  the  withdrawal  of  the  filtrate  at 
pleasure. 


WASHING.  513 

CHAPTER  XXVII. 

WASHING. 

»v 

IN  all  precipitations,  the  powder  thrown  down  becomes  involved 
•with  more  or  less  of  the  original  liquid  from  which  it  has  been 
deposited.  As  these  liquid  portions  are  impurities,  they  must  be 
separated ;  and  in  many  large  operations,  and  when  the  precipi- 
tate is  bulky,  we  effect  their  removal  by  repeated  washing  and 
DECANTATION  ;  but  when  the  powder  is  light,  and  in  all  cases 
where  accuracy  in  estimating  results  is  required,  the  purification 
is  conducted  by  pouring  continued  streams  of  water  or  other  fluid 
through  the  substance  contained  on  the  filter. 

Washing  by  decantation  is  usually  practised  by  diffusing  the 
precipitate  in  a  large  quantity  of  cold  or  hot  water,  or  other  suit- 
able liquid,  as  circumstances  may  require  or 
admit ;  stirring  well,  and  after  sufficient  re- 
pose for  settling,  decanting  the  clear  super- 
natant solution.     A  repetition  of  additions  of 
fresh  water,  and  subsequent  decantations  after 
repose,  will  entirely  remove  all  soluble  matter 
and  free  the  precipitate  from  impurity. 

In  analyses,  the  precipitate  is  most  gene- 
rally washed  upon  the  filter  by  projecting 
water  from  the  spritz  bottle  A,  Fig.  426,  the 
jet  of  which,  by  its  force,  at  the  same  time 
loosens  that  portion  adhering  to  the  sides, 
and  concentrates  it  all  at  the  bottom,  when  a 
larger  amount  of  washing  liquid  may  be  added  from  the  bottle, 
Fig.  55.  To  give  force  to  the  issuing  jet,  as  is  sometimes  neces- 
sary in  detaching  particles  from  the  filter,  the  tubes  of  the  spritz 
may  be  as  shown  in  Figs.  439,  440.  The  compression  of  the  air 
in  the  interior  by  blowing  in  the  tube  a  produces  a  jet  through 
the  lateral  one  5,  drawn  out  to  a  small  orifice.  This  form  of 
spritz  is  much  more  convenient  for  large  filters  than  the  smaller 
one,  Fig.  428;  either,  however,  allows  the  direction  of  the 
stream  to  any  desired  part  of  the  filter.  The  above-mentioned 

33 


514 


WASHING. 


bottle  is  flat-bottomed,  and  of  thin  glass,  so  as  to  answer  for  the 
use  of  boiling  liquid. 

Fig.  440. 


The  copper  flask,  Fig.  240,  with  tubes  fitted  to  its  mouth  as 
above  described,  is,  however,  far  more  convenient,  and  less  liable 
to  receive  injury. 

Fig.  441.  Fig.  442. 


The  precipitate  being  in  this  manner  kept  constantly  mingled 
with  liquid,  is  soon  freed  from  its  soluble  matter.  The  latter  fact 
is  known  when  a  drop  of  the  wash-liquor,  which  has  passed 
through,  leaves  no  stain  upon  a  silver  or  platinum  spatula  heated 
over  the  spirit-lamp. 


EDULCORATION— WASHING   BOTTLES.  515 

There  are  many  precipitates  which  require  protracted  washing, 
or  edulcoration,  as  it  is  sometimes  termed,  in  order  to  cleanse 
them  thoroughly,  and  the  bottle  for  the  purpose  is  so  con- 
structed as  to  be  self- operating  in  a  measure,  this  mode  being 
a  great  saving  of  time  and  labor  to  the  operator.  Fig.  441 
represents  the  whole  arrangement,  which  is  so  contrived  that 
by  a  suitably  constructed  tube  5,  adapted,  by  means  of  a  per- 
forated cork,  to  the  flask  or  bottle  a,  the  water  therein  contained 
flows  out  very  gradually,  and  in  quantity  proportional  to  its 
passage  through  the  filter.  The  tube  is  that  known  as  Berzelius's. 
It  may  be  well  replaced  by  two  separate  tubes,  which  can  be 
readily  formed  over  the  blowpipe  flame  by  the  operator  himself ; 
and  the  modified  implement  is  shown  at  Fig.  442. 

Below  are  the  two  forms  of  washing  tubes,  both  acting  upon 
the  same  principle.  Fig.  443  represents  the  one  devised  by  Ber- 
zelius,  and  Fig.  444  that  by  Gmelin. 

The  mode  of  washing  by  these  bottles  is  very  convenient. 
They  are  nearly  filled  with  water,  and  inverted  over  the  funnel 
in  such  a  position  that  the  part  c  extends  below  the  surface  of 
the  liquid  and  no  further.  The  flow  continues  in  a  constant  cur- 
rent without  further  attention  until  the  surface  of  water  in  the 
filter  rises  towards  the  line  e  /,  Fig.  444,  and  diminishes  the 
pressing  column,  when  capillarity  is  in  excess  and  no  more  water 
flows.  But  as  the  water  slowly  percolates  through  the  filter,  the 
column  is  increased,  and  the  water  again  flows.  This  alternate 
action  is  continued  until  the  bottle  is  emptied. 

The  great  convenience  of  this  arrangement  is  that  a  filter  may 
be  washed  during  the  absence  or  inattention  of  the  operator. 

If  the  precipitate  is  soluble  in  water,  it'  must  be  washed  with 
alcohol,  ether,  or  other  liquid,  which  is  without  action  upon  it. 

When  the  bottle  filled  with  water  is  inverted,  as  in  Fig.  441, 
there  will  be  no  efflux  of  water  from  the  small  opening  <?,  Fig. 
444,  so  long  as  this  point  is  at  a  certain  distance  below  the  curve 
of  the  syphon ;  but  if  the  moistened  finger,  or  other  body,  be 
held  to  the  point  c,  water  will  flow  freely  from  it,  and  air-bubbles 
will  ascend  through  i  b  to  supply  its  place.  If  the  tubes  and 
opening  were  of  large  size,  the  water  would  flow  out  with  touch- 
ing  the  end  of  the  tube;  but  being  of  small  diameter,  and  the 
end  c  being  drawn  out  finely,  the  efflux  of  water  is  opposed  by 


516 


EDULCORATION — WASHING   BOTTLES. 


capillary  attraction.  The  column  of  water  between  £/and$r  h 
is  the  force  tending  to  overcome  the  capillary  resistance.  If  this 
column  be  lengthened  by  drawing  c  d  further  through  the  cork, 


Fig.  443. 


Fig.  444. 


then  the  water  will  flow  out  of  e  spontaneously.  If  c  d  be  pushed 
in  just  so  far  that  the  water  does  not  flow  spontaneously,  then 
the  capillary  resistance  slightly  predominates.  Then  if  a  sub- 
stance to  which  water  adheres  by  adhesive  attraction,  be  applied 
to  the  end  of  c,  it  will  make  the  water  flow  so  long  as  it  is  held 
there,  because  the  adhesive  attraction  of  the  touching  overcomes 
the  capillary  action.  If  c  d  be  thrust  still  further  into  the  cork, 
then  capillary  action  predominates  so  greatly  that  no  adhesive 
force  can  counteract  it,  and  the  water  will  consequently  not  flow 
out.  There  is,  therefore,  a  particular  medium  position  for  the 
point  <?,  where  it  will  act  as  desired. 

For  other  than  analytic  operations,  the  washing  arrangement 
may  be  as  shown  by  Fig.  445. 

It  consists  of  a  wide-mouth  bottle,  with  two  perforations  in  the 
cork,  through  which  pass  the  bent  tubes  a  and  b.  One  of  those 
bent  tubes  descends  nearly  to  the  bottom  of  the  bottle,  as  at  c  ; 
the  other  stops  below  the  cork.  The  outer  legs  of  the  tubes  dip 
into  the  filter,  the  one,  5,  deeply,  and  the  other,  «,  just  under  the 
surface  of  the  contained  liquid.  The  apparatus  being  ready,  air  is 
to  be  drawn  through  the  tube  b  by  mouth  suction  at  the  end  until 


COOKE'S  WASHING  MACHINE.  517 

the  liquid  rises  and  flows  over  into  the  filter.     The  current  thus 
established  will  continue  until  the  level  of  the  liquid  in  the  funnel 


Fig.  445. 


is  uniform  with  the  end  c  of  the  tube  b  in  the  bottle,  and  then 
cease.  As  the  latter,  however,  falls  in  proportion  as  the  filtra- 
tion proceeds,  it  will,  of  course,  from  time  to  time,  open  the' 
mouth  of  the  tube  a,  and  the  air  entering  at  such  intervals  sup- 
plies the  pressure  necessary  to  preserve  the  continuity  of  the 
stream  of  liquid. 

As  it  is  very  frequently  requisite  to  wash  precipitates  with 
volatile  liquids,  J.  P.  Cooke  has  suggested  an  arrangement  for 
the  purpose,  which  combines  efficiency  with  simplicity  and  cheap- 
ness. It  is  also  applicable  for  continuous  filtration,  or  for  filtra- 
tion either  in  vacuo  or  in  an  atmosphere  of  any  gas  that  is  de- 
sirable. Moreover,  it  protects  the  filter  from  the  dust  and  fumes 
of  the  laboratory,  even  when  the  exclusion  of  air  is  not  essential. 

The  complete  arrangement  is  shown  at  Fig.  446  (1),  and  "con- 
sists of  a  wide-mouth  glass  bottle,  into  the  neck  of  which  is  firmly 
ground  with  emery  a  funnel  «,  having  a  short  but  large  spout. 
These  are  made  sufficiently  thick  to  resist  the  atmospheric  pres- 
sure, and  the  rim  of  the  funnel  is  ground  so  that  the  apparatus 
may  be  closed  air-tight  by  means  of  a  glass  plate.  Within  the 


518 


COOKE'S  ARRANGEMENT. 


outer  funnel  the  common  filtering  funnel  is  placed,  resting  loosely 
against  its  side,  so  as  to  allow  free  passage  of  air."     This  funnel 

Fig.  446. 


and  some  other  parts  of  the  apparatus  are  shown  in  enlarged 
views  at  2. 

"  In  order  to  wash  a  precipitate,  or  to  produce  a  vacuum  in 
the  interior  of  the  apparatus,  a  glass  plate,  with  a  hole  an  inch 
or  more  in  diameter,  drilled  through  its  centre  dj  is  substituted 
for  the  covering  plate.  Through  this  passes  the  tube  of  a  wash- 
ing-bottle/; and  this  washing-bottle  is  of  the  usual  construction, 
except  that  it  is  fitted  with  a  cork  which  projects  about  an  inch 
above  the  neck.  This  upper  end  of  the  cork  fits  the  neck  of  a  glass 
plate,  ground  on  the  under  side,  as  is  represented  at  e.  The  plate 
is  about  three  inches  in  diameter,  and  when  resting  on  the  plate  d, 
covers  the  opening  completely,  and  permits  sufficient  lateral 
motion  to  bring  the  stream  of  water  on  different  parts  of  the  pre- 
cipitate. A  vacuum  is  readily  obtained  by  connecting  the  appa- 
ratus with  an  air-pump  by  means  of  a  flexible  tube  having  a  brass 
plate  at  the  end  sufficiently  large  to  cover  the  opening  in  the 
plate  d,  and  by  an  easy  manipulation,  the  interior  may  afterwards 
be  filled  with  hydrogen  or  any  other  gas." 


CYLINDER   ELECTRICAL  MACHINE.  519 

CHAPTER   XXVIII. 

THE   PRACTICAL  RELATIONS  OP   ELECTRICITY. 

THIS  chapter  will  refer  to  the  most  ready  and  efficient  means 
of  developing,  detecting,  and  applying  electrical  action ;  and  will 
comprise  information  upon  the  practical  points  of  electricity 
excited  by  friction  as  in  the  use  of  the  electrical  machines ;  of 
electricity  evolved  by  chemical  means  as  in  the  working  of  the 
galvanic  battery ;  and  also  of  electricity  induced  by  magnetic 
force,  as  in  the  operation  of  electro-magnetic  apparatus. 

We  will  open  the  subject  with  instruction  as  to  the  manner  of 
developing  electricity  by  mechanical  action,  and  describe  the  most 
approved  forms  of  electrical  machines.  The  works  of  Faraday, 
De  La  Rive,  Hare,  Noad,  and  Smead,  will  afford  full  information 
upon  theoretical  points. 

The  Cylinder  Electrical  Machine  is  shown  in  Fig.  447.  A  is 
a  glass  cylinder,  the  axis  of  which  works  in  two  wooden  supports 

Fig.  447. 


fixed  vertically  in  a  solid  frame.  The  cylinder  is  made  to  revolve 
by  turning  a  winch  connected  by  a  crossed  band  to  a  wheel 
attached  to  one  end  of  the  axis  of  the  cylinder.  F,  the  negative 
conductor,  is  a  brass  tube  supported  by  a  glass  pillar,  and  has 


520  CYLINDER   ELECTRICAL   MACHINE. 

upon  the  side  nearest  the  glass  cylinder  the  rubber,  or  leather 
cushion,  which  presses  against  the  glass.  To  the  cushion  is 
attached  the  flap  of  silk  G,  which  extends  over  the  cylinder  nearly 
to  the  points  of  the  positive  conductor  c.  A  screw,  passing 
through  two  nuts,  is  so  placed  bejow  as  to  regulate  the  pressure 
of  the  rubber  upon  the  glass,  by  increasing  or  lessening,  as  may 
be  necessary,  the  distance  between  the  movable  pedestal  upon 
which  the  former  stands  and  the  main  supports  of  the  machine. 
At  the  opposite  side  of  the  cylinder  is  the  positive  or  prime  con- 
ductor c,  being  like  the  other  conductor  a  tube  of  metal,  and  also 
insulated  and  furnished  with  balls  for  the  transference  of  the 
electricity ;  but  having,  instead  of  a  rubber,  a  collector  E,  made 
hollow,  and  of  sheet  brass,  and  provided  with  sharp-pointed  pro- 
jections, which  almost  touch  the  surface  of  the  cylinder. 

This  machine  is  made  to  develope  electricity  by  turning  the 
winch,  which  causes  the  small  wheel  and  attached  cylinder  to  re- 
volve with  accelerated  rapidity.  By  the  friction  of  the  rubber, — 
covered  with  a  metallic  amalgam, — upon  the  glass,  the  electricity 
acquired  by  the  glass  is  decomposed,  its  positive^  element  remain- 
ing attached  to  the  glass,  and  its  negative  one  to  the  cushion. 
The  former,  prevented  from  escaping  by  the  non-conducting  flap 
of  silk,  is  carried  round  with  the  glass,  and, — after  a  series  of 
alterations,  by  induction,  of  the  equilibrium  of  that  portion  of  the 
fluid  naturally  present  in  the  conductor, — finally  by  passing  into 
it  through  the  highly  conducting  collector,  fills  it  with  positive  or 
vitreous  electricity,  which  can  be  drawn  off  from  it  into  other 
conducting  bodies,  either  insensibly  or  in  sparks.  The  negative 
conductor,  while  insulated,  becomes  in  the  same  way  negatively 
electrified,  and  is  capable  of  giving  sparks  to,  or  rather  receiving 
them  from,  other  bodies  oppositely  influenced ;  but  while  uncon- 
nected with  the  earth,  it  gives  off  but  a  small  amount  of  its  posi- 
tive component,  and  soon  returns  to  its  former  state  of  equili- 
brium from  its  negative  electricity  being  neutralized  by  the 
positive  kind  of  the  prime  conductor,  which  passes  back  over  the 
surface  of  the  cylinder,  and  which  also  reaches  it  by  other  sources 
of  imperfect  conduction. 

If  much  positive  excitement  is  desired,  the  conductor  to  which 
the  rubber  is  attached,  must  be  kept  in  connection  with  the  earth 
by  a  metallic  chain  or  wire.  When,  on  the  contrary,  the  object 


PLATE  ELECTRICAL   MACHINE* 


521 


is  to  obtain  negative  electricity  from  its  proper  collector,  the 
prime  conductor  must  be  made  to  communicate  with  the  earth  by 
similar  means. 

The  Plate  Electrical  Machine.— This  is  a  modification  of  the 
cylinder  machine,  and  is  preferable  on  account  of  its  simplicity 
and  greater  power.  In  damp  weather,  too,  it  is  much  more  reli- 
able and  efficient.  The  figure  shows  this  machine  in  its  details. 

Fig.  448. 


It  consists  of  a  circular  glass  plate,  from  one-twelfth  to  one-eighth 
of  an  inch  in  thickness,  and  varying  in  diameter  from  one  to  five 
feet.     The  plate  is  traversed  at  its  centre  by  a  metallic  axis, 
fixed  solidly  to  the  glass  by  two  clamp-nuts.     The  axis  rests  upon 
two  upright  wooden  supports  fixed  in  a  frame,  and  is  so  arranged 
as  to  hold  the  glass  in  a  central  position.     A  pair  of  cushions  is 
fixed  to  the  supports  above  and  below  the  axis,  and  so  placed  as 
to  exert  a  considerable  pressure  upon  the  plate.    A  rotary  mo- 
tion is  given  to  the  plate  by  a  glass  handle  attached  to  one  end 
of  the  axis.     Two  insulated  conductors,  joined  by  a  metallic  rod, 
are  placed  parallel  to  the  axis,  and  near  the  circumference  of  the 
plate.     One  end  of  each  conductor  encompasses  the  glass  plate, 
and  is  fitted  with  points  to  draw  off  the  electricity.     A  chain 
fastened  to  the  wooden  supports  serves  to  connect  the  machine 
with  the  earth.     As  thus  arranged,  the  plate  machine  only  fur- 


522  PLATE  ELECTRICAL  MACHINE. 

nishes  positive  electricity;  if  negative  electricity  is  required,  the 
conductors  must  be  made  to  communicate  with  the  earth  by  a 
chain;  and  if  negative  and  positive  electricity  are  needed,  it 
becomes  necessary  to  insulate  the  cushions. 

Great  care  is  requisite  in  the  construction  and  arrangement 
of  all  the  parts  of  the  electrical  machine.  The  quality  of  the 
glass  is  the  most  important  point.  It  should  be  well  annealed, 
strong,  smooth,  and  even.  The  best  glass  is  that  which  contains 
the  largest  amount  of  silica,  and  has  potash  for  a  base.  In  the 
cylinder  machine  all  moisture  must  be  carefully  expelled  from 
the  interior,  and  its  openings  hermetically  sealed  with  cement  or 
sealing-wax. 

The  cushions  are  pads  made  of  soft  (buckskin)  leather  stuffed 
with  horse-hair,  and  should  be  sufficiently  elastic  to  maintain  a 
strong  and  uniform  pressure. 

The  flap  attached  to  the  rubber,  of  ordinary  silk,  is  sometimes 
waxed. 

It  has  been  found  that,  in  order  to  render  the  exciting  power 
of  the  rubber  greater,  it  is  necessary  to  coat  the  cushions  with 
an  amalgam.  The  amalgam  of  tin  and  mercury,  used  for  making 
mirrors,  mixed  with  a  little  lard,  answers  the  purpose  very  well, 
or  bisulphuret  of  tin  (mosaic  gold)  may  be  used ;  but  the  best  is 
formed  by  adding  to  six  parts  of  heated  mercury  a  melted  alloy 
of  two  parts  of  zinc  and  one  of  tin,  and  triturating  the  whole  in 
a  mortar  until  cold.  This  amalgam  is  made  into  an  unctuous 
mass  with  tallow,  and  the  cushions  thoroughly  covered  with  it. 
The  cylinder  is  made  to  revolve,  and  the  excess  of  the  amalgam 
is  removed  with  a  cloth.  The  presence  of  little  specks  of  the 
amalgam  on  the  cylinder  appears  to  be  rather  beneficial  than 
otherwise. 

The  conductors,  in  order  to  preserve  the  electricity,  must  be 
cylindrical  and  rounded  at  the  ends,  and  otherwise  free  from  all 
angular  points  or  projections  other  than  the  points  which  conduct 
off  the  current  from  the  glass.  They  may  be  made  of  sheet  brass, 
or  of  wood  smoothly  covered  with  tin  foil.  The  supports  must  be 
good  insulators,  and  covered  with  a  varnish  of  shell-lac ;  and  they 
should  also  be  fixed  firmly  into  the  frame  of  the  machine  and  the 
conductors  themselves. 

Electrical  machines  are  most  effective  in  dry  and  cold  weather. 


THE  LEYDEN  JAR.  523 

Any  dampness  in  the  atmosphere  is  unfavorable  to  the  develop- 
ment of  electricity.  To  put  a  machine  in  good  order,  it  should 
be  carefully  freed  from  dust  and  moisture;  this  latter  is  best 
insured  by  exposure  of  the  machine  before  a  fire,  or  wiping  the 
glass  portions  with  a  cloth  moistened  with  ether.  Care  also 
should  be  taken  to  have  the  communication  of  certain  parts  with 
the  earth  as  perfect  as  possible ;  and  to  accomplish  this,  the  chain 
of  the  opposite  conductor,  from  which  it  is  desired  to  obtain  the 
electricity,  may  be  connected  with  the  water  or  gas  pipes  of  a 
house,  or  any  good  conducting  substance  which  penetrates  the 
moist  earth. 

When  the  machine  works  properly,  after  a  few  turns  of  the 
cylinder,  it  gives  off  a  vivid  spark  with  a  crackling  noise  upon  the 
approach  of  the  knuckle  or  a  metallic  ball  to  the  insulated  con- 
ductor. 

The  Ley  den  Jar. — This  apparatus,  as  shown  by  Fig.  449,  is 
employed  for  the  accumulation  of  electricity  by 
induction,  and  is  the  agent  chiefly  made  use  of  for        Fis-  449- 
laboratory  purposes.  It  consists  of  a  wide-mouthed 
thin  glass  jar,  varying  in  size,  neatly  coated  on  its 
inner  and  outer  surfaces  to  within  about  one  quar- 
ter of  its  height  from  the  top,  with  tin  foil.     The 
stopper  is  made  of  cork  or  dry  wood,  and  is  firmly 
inserted  and  well  varnished.     Through  its  centre 
passes  a  metallic  rod  terminating  on  the  exterior 
in  a  smooth  round  ball,  and  the  interior  in  a  point, 
or  bunch  of  diverging  wires,  communicating  with 
the  inner  coating.     The  ball  at  the  top  of  the  rod  should  be  at 
least  a  half  inch  in  diameter.     The  stoppers  and  uncovered  por- 
tion of  the  glass  should  be  thickly  covered  with  shell-lac  varnish. 
A  common  vial,  containing  iron  filings,  and  covered  on  the  out- 
side with  foil  up  to  the  level  of  the  metal  within,  and  provided 
with  a  rod  and  ball,  as  above  described,  makes  a  very  good  Ley- 
den  jar. 

In  order  to  charge  the  jar  the  electrical  machine  must  be  put 
in  motion,  and  the  jar  held  in  the  hand,  so  that  the  knob  touches 
that  conductor  of  the  machine  which  contains  the  kind  of  elec- 
tricity it  is  desired  to  collect  in  the  jar.  The  inner  coating  of  a 
Leyden  jar  is  easily  charged  with  negative  electricity  by  holding 


524  THE   LEYDEN   JAR. 

it  by  the  knob  and  putting  its  outer  coating  in  contact  with  the 
prime  conductor  of  the  machine.  When  charged,  it  is  necessary 
to  place  it  upon  an  insulated  table ;  for  if  touched  by  a  con- 
ducting medium,  it  would  cause  an  unpleasant  shock  to  the 
operator. 

The  electricity  often  accumulates  in  the  inner  coating  until 
its  tension  becomes  so  great  that  the  equilibrium  of  both  coat- 
ings is  restored  by  a  discharge  from  one  surface  to  the  other 
taking  place.  For  this  reason  it  is  not  safe  to  use  very  large  jars, 
as  any  imperfection  in  the  glass,  which  would  render  a  particular 
part  weaker  than  the  rest,  would  make  it  liable  to  fracture  by 
the  mutual  attraction  of  the  two  electricities,  which  would  effect  a 
union  by  breaking  the  glass. 

When  one  kind  of  electricity  is  collected  in  the  interior,  the 
opposite  sort  is  produced  in  the  exterior  coating,  or, — in  accord- 
ance with  the  theory  which  admits  the  existence  of  only  one  kind, 
— when  it  is  in  excess  in  the  inside,  it  is  deficient  in  the  same 
ratio  upon  the  outside.  The  tendency  is  then  always  to  restore 
that  neutrality,  or  natural  order  of  things  in  which  the  influence 
is  not  made  evident  to  the  senses ;  but  in  a  good  Leyden  jar,  the 
parts  should  be  so  arranged  as  to  permit  the  collection  of  a  large 
amount  of  electricity  before  a  spontaneous  discharge  takes  place. 
If  the  jar,  before  becoming  highly  charged,  permits  such  an 
escape,  it  is  usually  an  evidence  that  there  is  a  hole  or  crack  in 
the  glass,  that  the  uncovered  surface  has  become  a  partly  con- 
ducting one  from  the  presence  upon  it  of  moisture  or  dust,  or 
finally,  that  the  outer  metallic  coating  extends  up  so  far  as  to 
allow  of  the  easy  passage  of  a  spark  to  it  from  the  rod  or  ball. 
The  last  condition  can  be  altered  by  lessening  the  height  of  the 
outer  covering  of  foil,  taking  care  to  reduce  that  which  is  within 
also  to  the  same  level.  To  expel  moisture  and  dust,  the  vessel 
should  be  warmed  and  wiped,  as  before  directed  for  other  parts 
of  the  apparatus. 

The  retention  for  some  time,  of  the  charge,  by  the  Leyden  jar, 
is  often  a  matter  of  great  importance  in  the  chemical  applica- 
tions of  electricity.  A  jar,  of  the  capacity  above-mentioned, 
when  dry,  warm,  and  fully  charged,  should,  after  a  lapse  of  ten 
minutes,  give  a  spark  at  least  half  an  inch  in  length  to  the  ball 
of  a  discharging-rod,  the  ball  being  one-third  of  an  inch  in  dia- 
meter. 


THE   ELECTRICAL  BATTERY. 


525 


The  power  of  the  jar  is  dependent  on  the  amount  of  the  coated 
surface,  and  the  thinness  of  the  glass. 

The  Electrical  Battery.-^  is 'an  arrangement  b  ^^ 
the  metallic  surfaces  of  the  Leyden  jar  are  greatly  increased  in 
size,  and  by  which  the  intensity  of  the  shock  and  discharge  is 
multiplied  to  almost  any  extent  desired.  A  number  of  Leyden 
jars,  prepared  in  the  usual  manner,  are  placed  in  a  box,  which  is 
lined  with  tin  foil  or  other  metallic  coating.  The  vessels  are 
placed  in  close  contact,  or  are  made  to  connect  with  each  other 
externally  by  the  interposition  of  metallic  or  coated  partitions, 
and  the  inner  coatings  are  made  to  communicate  by  means  of 
metallic  rods  or  chains,  connected  with  the  wires  going  from 
their  interior.  The  whole  is  equivalent  to  a  single  large  jar,  and 
may  be  charged  and  discharged  with  equal  facility.  (Fig.  450.) 

Fig.  450. 


The  hook,  seen  in  the  front  of  the  box  which  contains  the  series, 
is  attached  to  the  metallic  outer  lining. 

When  the  battery  is  to  be  used,  it  should  be  ascertained  that 
all  the  outside  coatings  are  in  proper  connection  with  each  other, 
and  that  the  inner  surfaces  communicate  through  their  appro- 
priate mountings  and  wires,  and  that  no  wires,  threads,  water,  or 
other  conducting  substances  extend  in  any  way  from  the  inner 
to  the  outer  parts  of  the  apparatus.  No  filamentous  or  pointed 
body,  or  projecting  piece  of  metal,  should  be  allowed  to  remain 
very  near  the  battery  while  it  is  in  operation.  The  battery  is 
charged  by  connecting  one  of  the  wires  or  knobs  which  are  in 
contact  with  the  inner  coating  of  the  jars,  by  means  of  a  chain 
or  wire,  with  the  prime  or  negative  conductor  of  the  electrical 
machine  while  it  is  in  operation.  It  is  both  filled  and  discharged 


526  THE   DISCHARGER. 

in  the  same  way  as  the  Leyden  jar,  and  all  its  operations  are 
those  of  that  vessel  upon  a  greater  scale. 

During  the  charging  of  a  battery,  a  diffusion  of  electricity 
sometimes  takes  place  over  that  part  of  the  uncoated  glass,  which 
is  near  the  edge  of  the  foil.  This  is  not  entirely  removed  upon 
the  discharge  of  the  coated  part,  but  afterwards  gradually  returns 
to  the  coating  and  recharges  the  battery,  often  to  a  considerable 
extent.  Hence,  if  after  the  discharge  of  a  battery,  it  be  left  for 
a  few  minutes  with  the  two  coatings  unconnected,  it  will,  upon 
the  application  of  the  discharger,  give  a  considerable  spark. 
This,  which  is  the  residual  charge,  is  discharged  in  the  same  way 
when  the  Leyden  jar  is  used. 

In  order  to  know  when  a  jar  or  battery  is  fully  charged,  the 
inner  coating  is  brought  in  contact  with  the  quadrant  electroscope, 
the  arc  described  by  the  repulsion  of  the  needle  of  which  shows 
the  relative  amount  of  electricity  in  the  jar  or  battery.  When 
the  angle  marked  by  the  needle  remains  constant,  or  reaches  to 
45°,  the  jar  is  filled  to  its  capacity. 

When  it  is  desired  to  cut  off  electric  communication  with  other 
bodies,  the  object  must  be  placed  upon  an  insulated  stool.  The 
latter  is  nothing  more  than  a  common  stool  with  strong  legs  of 
glass,  which,  being  non-conductors,  effect  the  insulation. 

A  plate  of  mica,  or  a  piece  of  dry  glass  plate,  laid  across  the 
top  of  a  glass  jar,  will  answer  as  an  insulating  plane.  It  should 
not  be  placed  upon  any  conducting  body,  because  of  the  influence 
it  may  receive  through  induction. 

The  Discharger. — A  discharge  between  the  oppositely  electri- 
fied surfaces  of  the  jar  may  be  effected  by  bringing  one  hand  in 
contact  with  the  external  coating,  and  touching  the  knob  with  a 
knuckle  of  the  other.  In  this  case  the  person  receives  a  shock 
in  his  arms,  and  if  the  surfaces  are  large  or  well  filled  with  elec- 
tricity, he  experiences  a  painful  passage  of  this  shock  through 
the  shoulders  and  chest.  A. battery  ordinarily  charged,  should 
never  be  discharged  in  this  way,  as  serious  and  even  fatal  results 
might  follow. 

The  instrument  shown  in  the  figure  is  called  a  discharger,  and 
is  used  to  complete  the  circuit  between  the  opposite  coatings  of 
both  the  jar  and  the  battery.  The  rods  R,  R,  are  so  united  with 
a  hinge  that  the  balls  may  be  made  to  come  in  contact  with  the 


THE  ELKCTROPHOKUS. 


527 


surfaces  or  to  be  removed  from  them  by  means  of  the  insulating 
glass  handles,  which  are  attached  to  the  legs.    This  arrangement 


Fig.  451. 


Fig.  452. 


gives  the  power  of  discharging  a  jar  of  almost  any  size,  by  re- 
moving or  approximating  the  handles.  A  very  effectual  and 
cheap  discharger  is  made  of  a  piece  of  thick  wire,  about  twelve 
inches  long,  curved,  and  terminated  by  a  bullet  at  each  end. 

The  Electrophorus. — This  important  instrument,  Fig.  452,  may, 
in  many  cases,  be  made  to  take  the 
place  of  the  common  electrical  machine. 
A  mixture  of  equal  parts  of  common 
resin,  shell-lac,  and  Venice  turpentine, 
is  melted  and  kept  in  a  state  of  fusion 
at  a  temperature  between  230°  and 
240°  of  Fahrenheit,  until  nearly  all 
evolution  of  vapor  has  ceased  and  the 

fluid  is  quiet.  It  is  allowed  to  cool  to  the  point  of  thickening, 
and  is  then  poured  carefully,  so  as  to  avoid  the  formation  of  air- 
bubbles,  into  a  circular  metallic  tray  or  dish,  of  about  nine  or 
twelve  inches  in  diameter,  and  half  an  inch  in  depth.  The  resi- 
nous surface  should  be  as  even  and  as  smooth  as  possible.  A 
wooden  box,  or  a  receptacle  made  by  placing  upon  a  smooth 
board  a  wooden  hoop,  are  less  costly,  and  do  not  expose  the  resin 


528  THE   ELECTROPHORUS. 

to  the  risk  of  cracking  from  the  sudden  contraction  of  the  metal, 
which  is  apt  to  occur  after  its  expansion  by  heat.  Upon  the 
smooth  surface  formed  by  the  cooled  mixture,  is  placed  a  metallic 
disk,  or  one  of  wood  smoothly  covered  with  tin  foil,  either  of 
which  is  provided  with  an  insulating  handle  of  glass  or  sealing- 
wax,  which  is  inserted  in  its  centre  above.  This  disk  should  be 
somewhat  less  in  diameter  than  the  surface  of  resin.  The  top 
has  usually  attached  near  its  edge  a  wire  terminating  in  a  metal- 
lic ball,  from  which  the  spark  is  taken. 

When  this  electrophorus  is  used,  the  cover  is  removed,  and  the 
surface  of  the  resin  having  been  dried  and  slightly  warmed,  is 
rubbed  or  wiped  briskly  with  a  piece  of  dry  flannel,  a  silk  hand- 
kerchief, or  the  fur  of  a  cat  or  hare's  foot.  After  excitation  by 
this  means,  the  cover  is  lifted  by  its  handle — also  dry — and  is 
replaced  upon  the  surface  of  the  resin.  A  spark  will  then  pass 
from  the  knob  of  the  cover  to  the  knuckle,  or  a  metallic  body 
held  near  it.  Upon  raising  the  cover  again,  another  spark,  of 
greater  intensity  than  the  first,  will  be  received.  A  spark  like 
the  first  will  be  emitted  by  the  knob  after  replacing  the  cover,  and 
again  upon  its  withdrawal  one  similar  in  character  to  the  second 
will  be  given  off,  and  in  this  way  the  experiment  may  be  repeated 
almost  indefinitely,  if  the  weather  is  favorable. 

The  action  of  the  machine  is  explained  in  this  manner.  The 
negatively  excited  cake  of  resin  acts  inductively  upon  the  elec- 
tricity inherent  in  the  cover,  attracting  and  combining  with  its 
positive  element,  and  repelling  its  negative  one,  which  accumu- 
lates in  the  upper  part  of  the  cover.  When  the  top  of  the  cover 
is  touched,  the  negative  electricity  escapes,  and  the  positive  re- 
mains in  combination  with  the  negative  kind  of  the  resin,  as  long 
as  the  latter  is  covered  by  the  metallic  plate.  But,  upon  lifting 
this  by  the  insulating  handle,  the  positive  excitement  is  in  its  turn 
set  free,  and  given  off  in  sparks  from  the  knob.  A  similar  suc- 
cession of  actions  goes  on  for  some  time,  and  the  instrument  has 
been  known  to  give  sparks  for  weeks  without  being  freshly 
excited. 

To  obtain  strong  positive  sparks,  it  is  necessary  to  touch  the 
cover,  when  on  the  resin,  with  a  finger  or  other  conducting  body, 
and  to  remove  it  before  raising  the  cover.  To  obtain  the  strongest 
negative  sparks,  the  cover,  when  raised,  should  be  discharged  of 


HENLEY'S   QUADRANT  ELECTROMETER.  529 

all  its  electricity,  by  touching  with  the  hand,  before  it  is  again 
placed  upon  the  surface  of  the  rosin 

DETECTION  OR  MEASUREMENT  OP  ELECTRICITY. -It  is  an 
established  fact  that  ordinary  annealed  glass  and  sealing-wax 
become  respectively  positively  and  negatively  excited  when  rubbed 
with a  piece  of  silk.  It  is  equally  well  determined  that  an  at- 
traction  exists  between  bodies  in  their  natural  state  and  electrized 
matter;  that  bodies,  in  a  similar  state  of  excitement,  repel  each 
other;  and  that,  on  the  other  hand,  bodies  oppositely  electrized 
attract  each  other.  Thus  it  is  that  we  are  enabled  to  apply  tests 
which  will  distinguish  the  kind  of  electrical  excitement  shown  bv 
various  substances. 

Instruments  for  this  purpose  are  called  electroscopes,  the 
simplest  form  of  which  consists  of  a  glass  rod  to  which  is  fixed  a 
thread  of  silk  suspending  a  pith  ball.  If  a  piece 
of  sealing-wax,  excited  by  rubbing,  is  brought 
near  this  ball,  the  ball  will  be  attracted  to  the 
sealing-wax,  and  after  having  touched  it  will  be 
repelled.  The  ball,  in  the  first  instance,  being 
attracted  by  the  negative  electricity  of  the  wax, 
after  having  come  in  contact  with  it,  becomes 
itself  negatively  electrized  and  is  repelled.  Any 
electrized  substance  brought  near  the  ball  will 
then  attract  it,  if  positively  electrized,  and  repel  it  if  in  a  negative 
state. 

Henley's  Quadrant  Electrometer.— This  instrument,  Fig.  454, 
chiefly  used  to  determine  the  amount  of  electricity  present  in  the 
conductor  and  in  the  Leyden  jar,  consists  of  a  semicircle 
of  ivory  or  of  wood  covered  with  white  paper,  which  is 
graduated  into  180  degrees,  and  fixed  at  its  base  to  a 
wooden  column.  In  the  centre  of  the  semicircle  there 
is  a  pin  upon  the  column,  from  which  a  movable  radius, 
terminated  by  a  pith  ball,  is  suspended.  The  column 
may  be  fixed  in  a  hole  in  the  conductor.  Upon  working 
the  machine,  the  column  and  the  ball  being  alike  affected,  the 
latter  with  its  radius  is  repelled  from  the  former,  and  by  the 
amount  of  the  divergence  the  force  is  exhibited  in  degrees.  By 
means  of  this  instrument,  we  are  enabled  to  ascertain  when  a  jar, 
or  battery,  in  contact  with  the  conductor,  is  sufficiently  electri- 

f\  A 


530  BENNET'S  ELECTROMETER. 

fied.  During  the  accumulation  in  the  inner  coating,  the  elec- 
tricity is  retained  forcibly  by  the  attraction  of  the  contiguous  and 
oppositely  electrified  surface,  and  will  not  be  given  off  to  an  insu- 
lated body,  or  one  which  is  not  in  connection  with  the  outer 
coating.  But,  in  proportion  as  it  ceases  to  be  retained  by  this 
inductive  action,  and  accumulates  in  the  conductor,  it  raises  the 
index  of  the  electrometer,  often  to  a  considerable  height.  When 
a  battery  has  received  its  greatest  amount  of  charge,  the  ball 
seldom  rises  above  40°  or  50°,  as  the  tension  of  the  electricity 
never  equals  that  of  a  single  jar,  probably  on  account  of  the 
larger  surface  exposed  to  induction. 

Bennet's  Electrometer. — This  instrument,  more  properly  called 
an  electroscope,  as  it  detects  rather  than  measures  electricity,  is 

exceedingly  delicate  in  its  indications. 
Fig.  455.  jt  consists  in  part  of  a  glass  cylinder, 

which  may  be  similar  in  form  to  the  one 
shown  in  the  drawing.  A  circular  brass 
cap  c,  covers  tightly  the  vessel,  and  to 
its  centre  is  attached  a  metallic  rod, 
enclosed  in  a  glass  tube,  which  is  well 
varnished  with  shell-lac,  and  having 
attached  to  its  ends  two  slender  strips 
of  gold  leaf  hanging  parallel  to  each 
other.  Two  strips  of  tin  foil  T  T,  are 
pasted  upon  the  inside  of  the  glass,  with 
their  upper  ends  a  little  above  the  level 
$<i-A  of  the  depending  extremities  of  gold 
leaf,  and  their  lower  ends  connected  with  the  metallic  bottom  of 
the  glass  cylinder.  When  an  electrified  body  is  made  to  ap- 
proach the  cap  of  the  electrometer,  the  gold  leaves  will  diverge, 
and  if  the  excitement  be  sufficiently  powerful,  will  touch  the  tin 
foil,  and  then  return  to  their  former  state  of  rest. 

The  delicacy  of  Bennet's  electrometer  is  much  increased  by 
the  addition  of  two  metallic  disks,  one  having  its  centre  soldered 
to  the  side  of  the  cap  of  the  instrument,  being  in  a  perpendicular 
position,  and  the  other  being  attached  to  a  rod  which  is  connected 
with  the  metallic  foot  of  the  instrument  by  a  hinge,  so  that  it 
may  be  placed  parallel  to  the  other  disk,  and  so  near  as  almost 
to  touch  it  without  actually  doing  so.  The  presence  of  elec- 


BENNET'S  ELECTROMETER.  531 

tricity  in  the  metallic  cap  and  its  disk,  induces  the  opposite  kind 
in  the  contiguous  metal,  which  is  then  to  be  removed  a  few  inches 
from  its  former  position.  As  this  disk  is  connected  with  the 
base  of  the  instrument,  and  of  course  with  the  tin  foil  upon  the 
inside  of  the  glass,  that  becomes  also  oppositely  electrified  from 
the  cap,  the  connected  gold  leaves  of  which  diverge  to  a  much 
greater  degree  than  in  the  simple  instrument.  This  is  called  the 
condensing  electrometer. 

Bennet's  electrometer  is  the  one  in  most  common  use,  and 
many  circumstances  of  interest  in  reference  to  its  employment 
are  worthy  of  note,  particularly  those  connected  with  the  means 
of  ascertaining  the  kind  of  electricity  which  causes-  its  gold  leaves 
to  diverge. 

If  an  insulated  conducting  body  containing  electricity,  such  as 
the  prime  conductor  of  the  electrical  machine,  is  made  to  approach 
or  to  touch  the  cap  of  the  electrometer,  the  leaves  diverge  to  a 
greater  or  less  degree,  in  proportion  to  the  tension  of  the  elec- 
tricity in  the  body,  and  remain  separated,  gradually  returning  to 
their  former  position  as  the  influence  passes  off.     In  examining 
the  condition  of  a  body  supposed  to  be  highly  electrified,  care 
must  be  taken  not  to  make  it  approach  the  cap  too  rapidly,  as 
the  result  of  a  sudden  and  powerful  communication  of  the  agent 
is  very  often  the  immediate  separation  and  tearing  of  the  gold 
leaves.     When  a  non-conducting  body,  electrically  excited, — a 
piece  of  sealing-wax,  for  instance, — is  brought  near  to  or  in  con- 
tact with  the  top  of  the  instrument,  the  same  divergence  takes 
place ;  but  it  is  temporary,  as  upon  the  withdrawal  of  the  body 
the  leaves  come  together  again.     To  make  their  separation  as 
lasting  as  in  the  former  case,  it  is  necessary  either  to  allow  the 
body  to  remain  for  a  time  upon  the  cap,  or  to  rub  it  over  its  sur- 
face, so  that  it  may  communicate  its  electricity  from  a  number  of 
points.     So  far,  the  electricity  of  either  kind,  imparted  to  the 
cap,  has  been  that  of  conduction.     But  if  the  electrified  body  be 
held  so  near  to  the  cap,  as  just  to  cause  the  divergence  of  the 
leaves,  that  divergence  will  diminish  gradually  until  the  leaves 
finally  collapse.     If  now  the  body  be  removed  to  such  a  distance 
that  it  can  scarcely  affect  the  leaves,  they,  after  coming  together, 
will  often  gradually  diverge  as  before.     This  second  separation 
is  caused  by  induction,  and  when  it  occurs,  the  opposite  kind  of 


532          THE  VOLTAIC  PILE  ELECTROSCOPE. 

electricity  to  that  existing  in  the  body  will  be  found  to  be  pre- 
sent in  the  cap  and  leaves.  The  same  effect  is  produced  by 
touching  the  cap  with  the  hand,  while  the  leaves  are  diverging 
from  the  electricity  of  the  excited  body,  by  removing  the  hand 
after  the  collapse  occasioned  by  its  first  contact,  and  by  then 
withdrawing  the  electrified  body,  as  before,  to  a  greater  distance 
from  the  cap. 

It  is  well  known  that  a  piece  of  sealing-wax  rubbed  with  warm 
flannel  becomes  negatively  electrified,  and  that  a  glass  tube 
rubbed  with  a  silk  handkerchief  becomes  positively  affected. 
These  facts  present  us  with  the  means  of  determining  the  kind  of 
electricity  which  is  transferred  to  the  cap  and  leaves  of  Bennet's 
electroscope.  If,  after  the  leaves  have  been  made  to  diverge  by 
the  approximation  to  the  cap  of  an  excited  body,  the  presence 
upon  the  top  of  a  piece  of  rubbed  sealing-wax  makes  the  diver- 
gence greater,  the  electricity  in  the  body  is  negative.  If,  how- 
ever, the  leaves  approach  each  other  slowly,  or  collapse  at  once, 
the  electricity  is  more  or  less  positive.  In  the  same  way,  a  warm 
tube  of  glass,  rubbed  with  a  silk  handkerchief,  will  increase  the 
separation  of  the  positively  electrified  leaves,  and  diminish  or 
annul  it  when  they  are  negatively  excited. 

The  Voltaic  Pile  Electroscope. — This  was  invented  by  Bohnen- 
berg.      It   consists   of  two   dry   voltaic 
Flg>  456-  piles,  made  of  layers  of  paper,  tinned  on 

one  side,  and  covered  with  a  thin  coat  of 
peroxide  of  manganese  on  the  other.  The 
manganese  is  made  to  adhere  by  forming 
it  into  a  paste  with  milk  and  starch.  The 
paper  thus  prepared  is  cut  into  disks  and 
made  into  piles,  care  being  taken  to  ob- 
serve the  proper  order,  the  tin  and  man- 
ganese being  always  in  contact.  The 
piles  are  fixed  on  a  stand  about  four 
inches  apart,  and  each  is  terminated  by 
a  metal  ball  of  the  same  diameter  as  the 
disks.  The  order  of  the  disks  is  so  ar- 
ranged that  the  upper  poles  of  the  two  piles  are  respectively  posi- 
tive and  negative ;  the  manganese  being  the  positive  element. 
The  whole  is  covered  by  a  bell  glass,  through  the  top  of  which  is 


COULOMB'S  ELECTROMETER. 


533 


Fig.  457. 


inserted  a  metal  wire  having  attached  to  its  lower  end  a  piece  of 
gold  leaf,  which  hangs  exactly  between  the  poles  of  the  two  piles. 
This  forms  a  very  sensitive  electroscope,  and  indicates  the  kind 
as  well  as  presence  of  the  electrical  excitement 

Coulomb's  Electrometer. -K\\  the  instruments  previously  de- 
scribed indicate  the  presence  of  electricity,  but  afford  little  idea 
of  its  quantity.     Coulomb's  torsion  balance  gives  us  a  means  of 
measuring  it  with  approximate  exactness ;  or  rather  of  comparing 
the  amount  of  it  found  in  one  body  with  that  existing  in  others 
or  in  the  same  body  at  different  times.    This  instrument,  as  repre- 
sented  in  Fig.  457,  consists  of  a  slender  beam,  or  thread,  of  shell- 
lac  B,  having  a  gilt  pith  ball  attached  to  one  end,  and  a  little 
vane  of  paper  to  the  other,  and  suspended  at 
its  centre  by  a  fine  metallic  wire,  or,  what  is 
better,  a  delicate  filament  of  spun  glass.    This 
ascends  in  a  cylindrical  or  square  frame  of 
glass,  and  its  upper  end  terminates  in  a  key 
D,  furnished  with  an  index,  the  whole  being 
capable  of  moving  easily  in  the  centre  of  the 
circle  6r,  which  is  graduated  into  360°.     A 
rod  of  shell-lac  I7,  is  inserted  in  the  hole  H, 
and  is  prevented  from  falling  down  into  the 
glass  cylinder  which  surrounds  the  whole  ar- 
rangement, by  a  stop  at  E.     This  rod  termi- 
nates in  a  gilded  ball,  which  is  called  the 
carrier  ball,  as  it  is  used  to  convey  to  the 
electrometer   proper,  the   electricity  of  the 
excited  body.     When  this  instrument  is  to  be  used,  the  rod  F  is 
brought  into  contact  with  the  excited  body ;  its  ball  acquires  some 
of  the  electricity,  and  upon  being  placed  in  the  cage,  it  gives  a 
part  of  it  to  the  ball  of  the  lac  beam.     This  having  now  the  same 
kind  of  electricity,  is  repelled  from  the  ball  of  the  rod,  and  de- 
scribes a  certain  angle  to  its  former  position,  which  it  retains 
until  it  loses  its  electricity.    To  measure  the  amount  of  fluid  thus 
acquired,  the  key  D,  to  which  the  glass  thread  is  fastened,  must 
be  turned  around,  until  by  the  torsion  or  twisting  of  the  latter, 
the  ball  of  B  is  made  to  come  in  contact  with  that  of  F.     The 
number  of  degrees  described  by  the  index,  which  is  attached  to 
the  revolving  key  D,  gives  an  approximation  to  the  proportion 


534  LANE'S  DISCHARGING  ELECTROMETER. 

of  electricity  derived  from  the  contact  of  the  ball  of  F  with  the 
electrified  body. 

A  more  simple  form  of  this  electrometer,  and  the  one  ordi- 
narily described,  consists  of  a  lac  needle  with  a  gilt  ball  at  each 
end,  suspended  by  means  of  a  fine  untwisted  thread  of  raw  silk, 
which  is  fixed  at  top  to  a  micrometer,  by  means  of  which  it  can 
be  turned  around  any  number  of  degrees  required.  The  whole 
is  encased  in  a  glass  vase  or  cylinder,  with  a  tightly-fitting  top 
of  glass,  through  a  hole  in  the  centre  of  which  the  silk  passes, 
the  micrometer  being  above.  Upon  the  level  of  the  suspended 
needle,  a  hole,  drilled  through  the  sides  of  the  glass,  encloses  a 
wire  having  a  metallic  ball  at  either  end,  the  inner  one  being 
nearly  in  contact  with  one  of  the  pith  balls.  The  excited  body 
is  made  to  approach  the  outer  ball,  and,  as  in  the  instrument 
before  described,  the  movable  knob  separates  from  the  other,  and 
the  quantity  of  electricity  is  proportional  to  the  distance  to  which 
it  is  driven  off. 

Lanes  Discharging  Electrometer.  —  This   instrument  is  for 
indicating  the  intensity  of  a  charged  jar  or  battery.     Its  con- 
struction is  shown  in  Fig.  458.     A  glass 
arm,  fitted  in  the  cover  of  the  Leyden 
jar,  has  a  hole  in  its  upper  end,  on  &  line 
with  the  ball  of  the  jar,  through  which 
passes  a  metallic  rod,  terminated  at  each 
end  with  a  ball  similar  to  the  one  of  the 
jar.     The  outer  ball  communicates  by  a 
chain  with  the  external  coating  of  the  jar, 
and  the  inner  is  advanced  to  the  ball  of 
the  jar  until  near  enough  to  receive  the 
spark.     The  intensity  of  the  charge  is 
shown  by  the  distance  at  which  the  dis- 
charge takes  place.     Of  course,  in  the  comparison  of  batteries, 
the  result  is  only  relative  when  made  under  a  like  condition  of 
the  atmosphere. 

Calorific  Electrometer. — "  The  effect  of  the  electrical  discharge 
on  metallic  bodies  is  to  raise  their  temperature  to  a  greater  or 
less  degree,  and,  in  many  instances,  to  render  metallic  wires  red- 
hot,  and  to  dissipate  them  in  a  shower  of  melted  globules.  The 
fusion  of  wire  has  accordingly  been  resorted  to  as  a  measure  of 


THE   GALVANOMETER. 


535 


Fig.  459. 


the  force  and  extent  of  electrical  accumulations  on  coated  glass. 
Independent  of  the  uncertainty  and  tediousness  of  this  method, 
it  is  quite  inapplicable  for  nice  investigations.  The  calorific 
electrometer,  whilst  it  avoids  all  destruc- 
tion of  the  metal,  indicates  at  the  same 
time  the  comparative  heating  effect  of  the 
discharge,  and  admits  of  an  accurate 
estimation  of  the  force  in  operation.  It 
consists  of  an  air-thermometer,  Fig.  459, 
having  a  fine  wire  of  platinum  passed 
air-tight  across  its  bulb,  which  is  screwed 
also  air-tight  on  a  small  open  vessel  con- 
taining a  colored  liquid,  and  soldered  to  the 
extremity  of  a  bent  glass  tube.  The  long 
vertical  leg  of  this  tube  is  supported  by 
a  graduated  scale  of  inches  and  tenths, 
on  a  convenient  foot,  the  lower  part  of 
which  is  marked  zero,  at  the  point  where 
the  colored  liquid  in  the  short  leg  finds  its  level.  There  is  a 
small  screw- valve  on  the  top  of  the  ball,  to  admit  of  an  opening 
with  the  external  air,  so  as  to  adjust  the  fluid  to  zero. 

"  When  an  electrical  accumulation  from  a  jar  or  battery  is 
passed  through  the  wire  in  the  ball,  the  temperature  of  the  wire 
is  more  or  less  raised,  which  causes  the  air  to  expand  and  press 
the  colored  fluid  up  in  the  long  leg,  the  altitude  being  measured 
on  the  graduated  scale.  In  this  way,  a  comparative  numerical 
value  of  the  heating  effect  of  the  discharge  may  be  arrived  at; 
and  it  is  found  that  the  height  to  which  the  fluid  rises  in  the  long 
leg  is,  cceteris  paribus,  as  the  square  of  the  quantity  of  electricity 
discharged  through  the  wire.  The  delicacy  of  this  electrometer 
will  depend  on  the  size  of  the  platinum  wire,  which,  for  ordinary 
purposes,  may  be  from  one-fiftieth  to  the  joo^h  of  an  inch  in  dia- 
meter, and  about  three  inches  in  length,  corresponding  with  the 
diameter  of  the  ball  of  the  thermometer." 

The  Galvanometer.— This  is  an  instrument  for  detecting  the 
electricity  developed  by  chemical  or  galvanic  action.  If  a  com- 
mon magnetic  needle,  supported  upon  its  pivot,  be  placed  directly 
under  and  parallel  to  a  wire  which  is  connected  with  the  poles  of 
a  galvanic  circuit,  so  that  the  positive  fluid  will  pass  through  the 


536  THE   GALVANOMETER. 

wire  from  the  north  to  the  south,  it  will,  during  the  passage  of 
the  current,  leave  its  position  in  the  magnetic  meridian,  and, 
after  a  few  oscillations,  assume  one  nearly  or  quite  at  right 
angles  to  it,  its  northern  end  or  austral  pole  pointing  to  the  east, 
or  to  some  point  between  it  and  the  north.  Precisely  the  same 
effect  will  be  produced  if  the  needle  is  placed  over  the  wire,  and 
if  the  direction  of  the  current  is  reversed.  But  the  northern  end 
will  be  turned  towards  the  west,  if  the  current  is  passed  from  the 
north  to  the  south  while  the  wire  is  under  it,  and  also  in  the 
same  direction  if  the  wire,  again  placed  over  it,  transmits  the 
fluid  from  the  south  to  the  north.  The  needle  always  returns  to 
its  former  position  immediately  after  disconnecting  the  wire. 
The  power  possessed  by  a  galvanic  current  of  influencing  the 
magnet,  may  be  increased  to  almost  any  extent,  by  passing  it 
through  a  number  of  wires,  or  a  coil  made  of  a  single  one,  so  as 
to  make  the  action  of  the  whole  equivalent  to  the  sum  of  the  ac- 
tions of  all  its  spires.  This  can  be  done  most  effectually  by  bend- 
ing a  long  wire,  covered  with  cotton  or  silk,  to  prevent  the  lateral 
escape  of  the  current,  into  the  form  of  a  rectangle.  The  needle 
is  supported  parallel  to,  and  between  its  horizontal  branches,  and 
it  is  obvious  that  it  will  be  similarly  affected  by  each  part  of  the 
coil,  in  whatever  position  its  wires  may  be;  for,  as  before  stated, 
a  current  passing  above  it  from  the  north  to  the  south,  and  one 
passing  below  from  the  south. to  the  north,  cause  it  to  deflect  in 
the  same  direction.  This  instrument  is  the  galvanometer,  or  the 
"electro-magnetic  multiplier,"  of  Schweigger.  By  its  use  we  can 
detect  traces  of  electricity  much  too  mi- 
;  ,,,  Fig.  460.  nuj.e  to  acj.  on  tke  gold-leaf  electrometer; 

tmt  its  chief  applications  are  to  the  dis- 
covery  of  delicate  galvanic  currents,  and 
to  the  determination  of  their  direction. 
As  shown  in  the  figure,  460,  it  consists  of 
the  coil  of  covered  copper  wire  N  B  s,  containing  usually  about 
twenty  convolutions,  of  which  the  extremities  are  connected  with 
the  cups  c  z.  A  card,  graduated  into  360°,  is  fixed  to  the  board 
A,  so  that  a  line  drawn  between  the  numbers  360  and  180,  coin- 
cides with  the  direction  of  the  centre  of  the  coil.  Above  this  is 
placed  a  delicate  magnetic  needle,  supported  on  a  pivot.  The 
coil  is  placed  with  its  long  axis  in  the  magnetic  meridian.  If 


ASTATIC  GALVANOMETER. 


537 


any  source  of  feeble  electricity  is  now  connected  with  the  cups, 
the  current  from  it  will  pass  through  the  coil,  and  the  magnet 
will  move  to  the  east  or  west,  according  to  the  direction  of  the 
fluid.  The  intensity  of  the  influence  is  estimated  in  degrees,  by 
comparing  the  position  of  the  utmost  divergence  of  the  needle 
with  the  number  under  it  on  the  card.  The  delicacy  of  this  in- 
strument depends  in  a  great  measure  upon  the  number  of  convo- 
lutions of  wire.  Thus,  if  all  other  circumstances  are  favorable, 
it  may  be  supposed  that  one  consisting  of  one  hundred  turns  will 
detect  an  amount  of  electricity  which  is  only  one-fifth  as  great  as 
that  shown  by  the  one  with  twenty  convolutions. 

The  Astatic  G-ahanometer. — The  sensibility  of  the  common 
galvanoscope  may  be  almost  indefinitely  increased  by  connecting 
the  magnetic  needle  immovably  with  another  one  placed  above 
the  rectangular  coil  of  wire,  but  parallel,  and  opposed  in  the 
direction  of  its  poles  to  tjie  first.  They  are  fastened  by  their 
centres  to  a  common  axis,  which  revolves  freely  in  an  aperture 
of  the  upper  branch  of  the  coil.  This  axis  is  suspended  by  a  fibre 
of  silk  to  the  upper  part  of  the  glass  or  other  vessel  in  which  the 
whole  is  encased,  and  it  penetrates  a  graduated  card,  placed 
under  the  upper  needle.  This  arrangement  makes  the  needle  a 

Fig.  461. 


balance  of  torsion,  the  movements^  which  are  compared  with  the 
degrees  marked  upon  the  card,  in  the  same  way  as  in  the  simple 
multiplier.     Terrestrial  magnetism  has  scarcely  any  effect  upon 
this  system  of  needles,  and  would  have  none  at  all  if  both  po| 
sessed  an  equal  amount  of  magnetic  power,  the  tendency  o 


538  ASTATIC  GALVANOMETER. 

one  to  assume  its  position  in  the  meridian  being  in  that  case  en- 
tirely counteracted  by  the  reversed  direction  of  the  other.  By  a 
reference  to  the  statements  at  the  head  of  this  article,  it  will  be 
seen  that  a  current  passed  through  the  coil,  in  either  direction, 
will  have  the  same  effect  upon  both  needles.  Fig.  461  represents 
two  of  the  many  forms  of  Nobili's  galvanometer.  It  is  called 
astatic  because  it  is  unaffected,  or  nearly  so,  by  the  magnetism 
of  the  earth. 

As  these  instruments  are  used  not  only  to  detect  currents,  but 
also  to  ascertain  the  directions  in  which  they  pass  through  the 
wires,  it  is  important  to  impress  upon  the  mind  the  movements 
of  the  needles  which  indicate  that  one  or  other  extremities  of  the 
coil  is  in  connection  with  the  positive  or  negative  electric  poles. 
A  simple  aid  to  the  memory  is  to  suppose  that  a  current  is  pass- 
ing around  the  middle  of  a  watch,  from  the  handle  over  the  face, 
and  is  returning  back  to  its  place  of  origin.  The  minute-hand, 
if  pointing  to  the  hour  twelve,  which  is  usually  placed  next  to 
the  handle,  may  be  supposed  to  represent  the  northern  half  of 
the  needle.  It  would  then  move  around  in  its  usual  direction 
towards  the  figure  three.  If  the  current  were  passed  around  the 
back  of  the  watch  from  the  handle,  and  returned  to  the  face,  the 
hand  would  move  backwards  towards  the  figure  nine.  Ampere 
has  devised  the  following  formula,  which  is  still  better  calcu- 
lated to  impress  the  direction  of  the  deviations  upon  the  memory. 
"  Let  any  one  identify  himself  with  the  current,  or  let  him  sup- 
pose himself  to  be  lying  in  the  direction  of  the  positive  current, 
his  head  representing  the  copper,  and  his  feet  the  zinc  plate,  and 
looking  at  the  needle,  its  north  pole  will  always  move  towards 
the  right  hand."  The  person  must,  however,  suppose  himself  to 
be  lying  over  the  needle,  his  head  and  its  north  pole  being  both 
in  the  same  direction. 

The  needles,  notwithstanding  all  care  to  make  them  astatic, 
will  vary  in  their  magnetic  force.  Nobili  suggests,  in  order  to 
equalize  the  action  of  the  needles,  that  after  having  discovered 
which  of  the  poles  of  the  needles  are  most  highly  magnetized,  to 
abstract  a  portion  of  the  magnetism  by  touching  them  lightly 
with  the  opposite  pole  of  a  weak  magnet.  As  the  sensibility  of 
the  apparatus  depends  upon  the  needles  having  only  so  much 
directive  force  as  to  keep  them  in  a  fixed  position,  it  is  necessary 


DIFFERENTIAL   GALVANOMETER.  539 

to  adjust  them  carefully,  so  that  they  may  he  affected  hy  the 
feeblest  current. 

After  the  direction  of  the  current  is  once  ascertained  in  the 
instrument,  to  avoid  delay  and  the  annoyance  of  repeating  the 
operation,  it  is  best  to  mark  it  upon  the  card. 

Differential  Galvanometer.— An  instrument  for  comparing  the 
•force  of  two  currents.  It  is  made  by  forming  simultaneously  into 
a  coil  two  wires  exactly  similar  in  diameter,  length,  and  every 
respect ;  and  arranging  the  needles  so  that  when  two  equal  and 
opposite  currents  are  passed  through  the  wires  they  will  exactly 
neutralize  each  other,  and  bring  the  index  to  0°.  But  when  un- 
equal currents  are  compared,  the  needles  will  indicate  the  direc- 
tion of  the  currents  and  their  relative  intensity. 

Galvanometers  of  this  sort  differ  only  in  the  length  and  size  of 
the  insulated  wires,  according  to  the  purposes  to  which  they  are 
to  be  applied.  Care  is  requisite  in  winding  the  coils  to  have  the 
wires  perfectly  insulated.  This  is  attained  by  gimping  them  with 
thick  silk,  and  interposing  a  coat  of  shell-lac  between  each  suc- 
cessive layer  on  the  coil.  In  the  case  of  galvanometers,  it  is  im- 
portant not  to  subject  them  to  currents  too  powerful  for  their 
capacity,  as  the  action  of  the  needles  is  apt  to  be  impaired  by  a 
diminution,  and  sometimes  even  of  an  inversion  of  their  mag- 
netism. 

Weygandt's  Galvanometer. — The  principal  novelty  of  this 
apparatus,  Fig.  462,  is  the  construction  of  the  pole-changer, 
which  gives  great  facility  in  working,  and  allows  the  coil  and 
divided  circle  to  be  turned  freely  around  without  altering  the 
position  of  the  pole-changer  or  disturbing  the  needle. 

This  instrument,  as  described  in  the  Franklin  Institute  Journal, 
No.  356,  rests  upon  a  flat,  circular  wooden  stand  (1),  about  nine 
inches  in  diameter,  which  is  supported  by  three  levelling  screws 
(2).  On  one  side  of  the  stand  are  the  two  binding-screws  (3), 
for  the  reception  of  the  wires  from  the  thermo-pile,  or  metals  to 
be  experimented  upon ;— the  wires  running  from  them  to  the  keys 
of  the  pole-changer,  which  is  situated  diametrically  opposite  to 
the  binding-screws  on  the  stand  (1). 

From  the  centre  of  this  stand,  rises  the  brass  centre,  upon 
which  the  circular  glass  box  (5),  containing  the  coil  and  gradu- 
ated circle,  turns  with  a  very  steady  motion.  The  two  needles 


540 


WEYGANDT'S  GALVANOMETER. 


Fig.  462. 


are  suspended  by  a  human  hair  from  a  hook  (6)  at  the  top  of  the 
instrument,  which  is  arranged  so  as  to  be  very  nicely  adjusted 
for  the  twist  and  for  its  height  in  the  coil. 

The  coil,  needles,  and  graduated 
circle,  are  enclosed  in  a  glass  box, 
the  plate  on  the  top  of  which  has  a 
small  hole  in  the  centre  through 
which  the  suspending  hair  passes; 
the  hair  being  protected  by  a  glass 
tube  (7),  the  top  of  which  is  sup- 
ported by  the  long  brass  standards 
(8),  which  carry  the  suspending 
hook.  By  this  arrangement  the  gra- 
duated circle  can  be  read  through  a 
plane  flat  glass,  instead  of  through 
the  side  of  the  glass  cylinder,  as 
frequently  constructed.  The  inner 
wire  of  the  coil  comes  down  to  a 
brass  ring,  which  is  fixed  to  the 
underside  of  the  bottom  of  the  re- 
volving-box. Concentric  with  this 
ring,  and  in  the  same  plane,  at  the 

distance  of  quarter  of  an  inch,  is  another  brass  ring  which  is 
connected  through  the  axis  with  the  wire  from  the  outside  of 
the  coil.  These  two  rings  thus  form  the  extremities  of  the 
coil,  and  the  pole-changer  plays  between  them.  The  wires 
from  the  binding-screws  are  attached  to  two  brass  slips,  which 
terminate  in  pieces  pressed  by  a  spring  against  the  inner  ring, 
so  that  when  the  pieces  are  in  their  normal  position,  the  current 
from  the  binding-screws  passes  through  the  short  space  of  ring 
between  them,  and  does  not  go  through  the  coil ;  but  when  either 
of  the  pieces  is  withdrawn  from  the  inside  ring,  and  pressed 
against  the  outside  ring,  the  current  passes  through  the  coil,  and 
by  altering  their  position  again,  bringing  that  one  which  was 
against  the  inside  ring  in  contact  with  the  outside  ring,  and  that 
which  was  in  contact  with  the  outside  against  the  inside  ring,  the 
direction  of  the  current  is  changed,  and  the  needle  deflected  in 
the  opposite  direction.  If  the  stand  is  placed  upon  the  table 


WEYGANDT'S  GALVANOMETER.  641 

in  a  position  which  is  convenient  for  the  operator,  with  the  keys 
of  the  pole-changer  near  his  right  hand,  the  coil  and  graduated 
circle  can  be  placed  in  any  position  without  interfering  with  the 
circuit,  as  some  part  of  the  brass  ring  must  always  be  opposite 
to  the  pole-changer. 

Each  key  of  the  pole-changer  works  like  the  writing  key  of  a 
telegraph ;  that  is,  it  is  depressed  by  the  finger,  and  returns  to 
its  position  by  the  spring  attached  to  it.  By  means  of  the  fore- 
finger and  second  finger  depressing  the  keys  alternately,  the 
direction  of  the  current  can  be  changed  six  or  eight  times  in  a 
second,  and  the  motion  being  in  a  vertical  plane,  is  little  liable  to 
affect  the  adjustment  of  the  instrument.  The  operator  has, 
therefore,  very  great  facility  in  bringing  the  needle  to  rest  by 
changing  the  circuit,  and  thus  checking  the  vibrations,  which 
enables  him  to  make  a  great  many  more  observations  in  a  short 
space  of  time  than  with  any  other  instrument  known. 

This  instrument  is  remarkable  for  its  delicacy,  as  was  confirmed 
by  the  following  tests. 

Two  pieces  of  zinc  and  bismuth,  each  about  the  size  of  an  ordi- 
nary type,  being  held  in  the  fingers  of  the  operator,  the  free  ends 
touching  the  binding-screws,  produced  an  instantaneous  and  steady 
deflection  of  175°. 

With  a  small  magnet,  weighing  about  half  an  ounce,  a  deflexion 
of  95°  was  produced,  at  the  moment  of  induction,  by  introducing 
the  magnet  into  the  coil. 

Two  wires  of  zinc  and  copper,  one-twentieth"of  an  inch  in  dia- 
meter, and  dipped  one-fifteenth  of  an  inch  into  a  single  drop  of 
Schuylkill  water,  gave  an  instant  deflexion  of  12°. 

With  a  small  Melloni  thermo-multiplier  of  twenty  pairs,  the 
heat  from  the  face  of  one  of  the  observers,  at  a  distance  of  eight 
feet,  gave  a  deflexion  of  68°. 

The  needle  can  be  brought  to  rest,  after  a  deflexion  of  90  ,  in 
a  very  few  seconds,  by  alternating  the  current  by  means  < 
pole-changers.  .. 

The  needles  are  remarkably  astatic,  having  a  very  small 
tive  power,  and  standing  steadily  in  an  east  and  west  position, 
with  a  slight  trouble  in  setting  them,    Mr.  Weygandt  mentions 
that  the  power  of  the  needles  was  balanced  by  rubbing  the 
stronger  one  lightly  upon  an  oil-stone,  which  appeared  to  weaken 


542  THE   COMMON   EUDIOMETER. 

without  removing  any  sensible  part  of  its  weight.  Altogether, 
the  instrument  is  very  remarkable  for  its  high  finish,  extreme 
delicacy,  and  great  convenience  in  use,  the  arrangement  of  the 
pole-changers  enabling  the  observer  to  make  many  observations 
in  a  short  time,  by  the  great  ease  in  bringing  the  needle  to  rest 
by  changing  the  current  rapidly. 

APPLICATIONS  OF  ELECTRICITY. — Electricity  proper  has  its 
most  general  application  in  the  chemical  analysis  of  gaseous  mix- 
tures, being  the  convenient  and  efficient  means  by  which  they  are 
exploded  and  decomposed.  It  is  employed  in  connection  with  the 
eudiometer,  an  instrument,  as  its  name  indicates,  chiefly  intended 
for  determining  the  purity  of  the  air,  but  by  means  of  which  other 
gases,  containing  carbon  and  hydrogen,  are  occasionally  examined. 
These  latter  are  made  to  unite  explosively,  in  it,  with  oxygen ; 
while  in  the  examinatioit  of  the  atmosphere,  the  explosion  of  hy- 
drogen with  its  constituent  oxygen,  and  the  consequent  produc- 
tion of  water,  and  diminution  of  volume,  enable  the  chemist  to 
determine  the  proportion  of  its  ingredients.  It  would  be  foreign 
to  our  purpose  to  give  a  full  description  of  all  the  applications  of 
eudiometry;  but  a  short  account  of  the  means  most  commonly 
employed,  particularly  in  reference  to  the  proper  mode  of  apply- 
ing the  electric  spark,  will  scarcely  be  at  variance  with  the  prac- 
tical nature  of  this  work. 

The  Common  Eudiometer  is  a  short  tube  of  thick  glass,  having 
one  end  closed.  This'  tube  is  graduated,  and  near  its  closed  ex- 
tremity, two  stout  wires  of  platinum,  or  other  metal,  intended  for 
the  transmission  of  the  spark,  are  inserted  in  the  opposite  sides, 
their  ends  inside  of  the  tube  being  a  short  distance  apart.  The 
other  end  of  the  tube  serves  for  the  introduction  and  escape  of 
the  gas,  and  it  remains  constantly  immersed  in  the  liquid  over 
which  the  experiment  is  made,  the  tube  being  supported  in  a  per- 
pendicular position.  The  gas  to  be  subject  to  the  spark  is  gene- 
rally such  a  mixture  as  will  inflame  explosively  at  once,  though 
sometimes  a  gradual  combination  of  some  of  its  elements  is 
effected  by  a  long-continued  succession  of  sparks.  The  tube, 
being  filled  with  water  or  mercury,  may  be  placed  over  the  trough ; 
or,  for  the  purpose  of  more  accurately  determining  the  level  of 
the  gas  in  the  way  about  to  be  described,  it  should  be  supported 
over  a  glass  vessel  containing  the  proper  liquid.  The  gases  are 


THE  COMMON  EUDIOMETER.  543 

then  successively  introduced  into  it,  in  the  proper  proportions, 
after  the  manner  heretofore  described.  To  determine  their 
volumes  with  the  utmost  degree  of  accuracy,  it  is  necessary  to 
support  the  tube  by  a  forceps  or  a  cork-lined  clamp,  as  repre- 
sented m  the  figure,  and  not  between  the  fingers,  so  that  their 

Fig.  463. 


temperature  and  volume  shall  not  be  increased  by  the  heat  of  the 
hand.     To  insure  that  the  gas  be  submitted  to  no  more  pressure 
than  that  of  the  atmosphere,  the  eudiometer  should  be  raised  in 
such  a  manner  that  the  interior  level  of  the  liquid  contained  in 
it,  shall  be  exactly  at  the  same  height  as  that  of  the  liquid  in  the 
vessel  outside.     In  order  to  secure  this,  it  is  necessary  that  the 
eye  of  the  observer  be  in  the  same  plane  as  the  two  levels  of  the 
liquid,  and  that  the  line  of  the  liquids  in  direct  contact  with  the 
glass  inside  and  outside  of  the  tube,  be  not  taken  as  the  proper 
standard.     It  must  be  recollected  that, — as  the  edge  of  a  surface 
of  water,  in  contact  with  the  glass,  is  elevated  above  its  true 
level  by  capillarity,  and  that  of  mercury  in  the  same  circumstances 
is  depressed, — the  lower  line  in  the  former  case,  and  the  upper 
one  in  the  latter,  will  give  the  true  position  of  the  main  surfaces. 
The  exterior  of  the  tube  is  now  wiped  clean,  so  that  no  mercury 
or  water  in  contact  with  the  wires,  can  conduct  off  the  electricity. 
The  tube,  kept  upright,  should  then  be  clasped  firmly  in  the  hand 
by  its  middle,  and  its  lower  end,  still  under  water,  should  be 
closed  with  slight  force  by  the  thumb  or  a  finger  of  the  unoccu- 


544  THE  COMMON   EUDIOMETER. 

pied  hand.  This  permits  the  descent  of  the  fluid,  which  is  driven 
out  by  the  force  of  the  explosion,  while  it  does  not  allow  its  too 
sudden  return  upon  the  subsequent  contraction  of  the  gaseous 
contents  of  the  tube,  or  the  escape  of  any  of  the  latter. 

In  using  the  eudiometer,  we  must  take  into  account  the  relative 
degree  of  explosibility  of  different  mixtures.  Thus  a  mixture  of 
oxygen  and  carbonic  oxide  expands  when  inflamed,  much  less 
than  one  of  oxygen  and  hydrogen  or  olefiant  gas.  A  large 
quantity  of  any  mixture  will  of  course  increase  in  bulk  much 
more  than  a  small  one.  The  whole  quantity  of  gas  contained  at 
first  in  the  tube,  should  be  at  least  so  small,  that  after  expansion 
it  shall  not  occupy  quite  the  whole  of  the  eudiometer.  No  more 
gas  should  be  introduced  for  detonation  than  will  occupy  a  sixth 
of  its  capacity  at  common  temperatures,  and  generally  it  will  be 
advisable  to  employ  much  less. 

The  spark  which  is  intended  to  effect  the  detonation  or  slow 
union  of  the  gases  contained  in  the  tube,  may  be  derived  from 
the  electrophorus,  the  prime  conductor  of  the  electrical  machine, 
or  the  Leyden  jar,  the  power  of  the  last  two  being  of  course 
greater,  in  the  order  in  which  we  have  spoken  of  them,  than  that 
of  the  first.  When  the  electrophorus  is  employed,  one  of  the 
wires  upon  the  side  of  the  eudiometer  is  placed  in  connection 
with  a  finger  of  an  assistant,  or  with  a  metallic  chain,  the  other 
end  of  which  hangs  in  the  trough  or  vessel  over  which  the  tube 
is  supported.  The  ball  of  an  excited  electrophorus  is  then  brought 
near  to  the  other  wire,  and  the  spark  obtained  from  it,  passing 
from  wire  to  wire  through  the  interior  of  the  tube,  inflames  the 
mixture,  if  it  be  of  sufficient  intensity,  and  if  all  the  other  cir- 
cumstances are  favorable.  The  ball  upon  the  conductor  of  the 
electrical  machine  may,  in  the  same  way,  be  made  to  approach 
one  of  the  wires,  with  usually  a  more  powerful  effect.  The  em- 
ployment of  the  electrical  machine  is  particularly  advantageous 
when  it  is  desired  to  pass  a  succession  of  sparks  for  a  consider- 
able time  through  the  mixture,  for  the  purpose  of  effecting  a  gra- 
dual combustion  or  combination  of  the  gases  contained  in  the 
tube.  The  use  of  the  Leyden  jar  is  equally  convenient  for  a 
single  contact,  and  much  more  apt  to  be  attended  with  success, 
on  account  of  the  greater  size  and  force  of  the  spark.  One  of 
the  wires  may  be  connected  with  the  external  coating  of  the  jar, 


URE'S  EUDIOMETER.  545 

by  means  of  a  chain  or  hooked  wire,  and  a  discharger  or  other 
conductor,  applied  at  one  end  to  the  ball  of  the  vial,  may  be 
brought  near  the  other  wire.  When  other  means  of  connection 
are  not  at  hand,  the  operator,  at  the  risk  of  receiving  an  unplea- 
sant shock,  may  grasp  the  jar  in  his  hand,  and  apply  its  ball  to 
one  wire  of  the  eudiometer,  while  he  touches  a  finger  of  the  other 
hand  to  the  opposite  wire.  To  insure  the  explosion  of  the  mix- 
ture, a  spark  of  the  largest  size  that  can  be  obtained  from  the 
electrical  instrument,  should  be  passed  through  it.  Very  often, 
although  a  sufficient  amount  of  electricity  is  given  off  from  the 
conductor  of  the  electrophorus  or  electrical  machine,  its  effect  is 
lessened  by  its  communication  from  wire  to  wire,  as  an  electrical 
brush,  or  in  a  succession  of  small  sparks.  To  remedy  this  evil, 
a  ball,  half  an  inch  or  more  in  diameter,  should  be  placed  upon 
the  outer  extremity  of  that  wire  which  is  to  receive  the  spark, 
and  the  latter  should  always  be  given  off  from  the  surface  of  a 
ball  of  considerable  size. 

The  wires  of  the  eudiometer  must  be  firmly  fitted  in  their 
places,  and  the  openings  in  the  glass  through  which  they  enter 
should  be  hermetically  closed  around  them.  Before  filling  the 
tube  with  gas,  it  must  also  be  ascertained  that  they  are  perfectly 
insulated.  When  the  detonation  is  effected  over  water,  a  film  of 
it  is  apt  to  adhere  to  the  glass  and  wires,  both  internally  and 
externally,  which,  by  its  conducting  power,  sometimes  diminishes 
the  force  of  the  spark,  or  intercepts  it  entirely.  To  prevent 
this,  the  outside  of  the  tube  and  wires  must  be  wiped  as  dry  as 
possible  before  applying  the  conductor.  The  top  of  the  tube 
should  be  gently  tapped  so  as  to  shake  off  any  particles  of  mois- 
ture adhering  to  it  within.  The  perfect  transmission  of  a  large 
spark  is  only  secured  by  the  presence  of  the  balls  upon  the  ends 
of  the  wire  and  discharger,  as  before  described. 

Ures  Eudiometer. — Analysis  of  gases  by  explosion  is  much 
more  conveniently  performed  by  means  of  Dr.  Tire's  syphon 
eudiometer,  shown  in  Fig.  464.  It  differs  from  the  other  eudio- 
meter in  being  curved  like  the  letter  U ;  but,  like  it,  it  has  the 
part  intended  to  contain  the  gaseous  mixture  graduated  and 
pierced  by  two  platinum  wires.  It  is  usually  about  twenty  inches 
in  length,  and  the  third  of  an  inch  in  internal  diameter.  This 
instrument,  like  the  other,  may  be  used  for  the  analysis  of  va- 

35 


546  URE'S  EUDIOMETER. 

rious  gases  over  either  water  or  mercury,  but  it  is  applied  chiefly 
to  that  of  atmospheric  air  over  the  latter  liquid :  and  we  will  con- 
fine ourselves  to  a  short  account  of  this  em- 
Fig.  464. 

ployment  of  it.     When  about  to  be  used  for 

an  examination  of  the  atmosphere,  it  is  filled 
with  mercury,  and  the  required  amount  of  air 
is  introduced  into  the  open  end,  which  is  in- 
verted over  the  trough,  as  in  the  case  of  the 
use  of  the  other  form  of  the  tube.  This  end 
is  then  tightly  closed  with  the  finger,  and  the 
tube  is  turned  slowly  so  as  to  admit  the  air 
into  the  graduated  extremity.  The  instru- 
ment is  then  held  upright,  and  the  amount  of 
air  introduced  is  read  off  by  looking  at  the 
scale,  after  subjecting  it  to  atmospheric  pres- 
sure by  displacing,  with  a  stick  thrust  in,  that  portion  of  mercury 
which  is  above  the  level  of  that  in  the  graduated  limb.  This 
having  been  accurately  done,  the  open  part  is  again  filled  with 
mercury,  closed  with  the  finger,  inverted  into  the  liquid,  and  an 
amount  of  pure  hydrogen  is  introduced  equal,  as  nearly  as  can  be 
guessed,  to  half  the  volume  of  the  air.  The  quantity  of  hydro- 
gen added  is  then  accurately  estimated  by  returning  the  eudio- 
meter to  the  erect  position,  equalizing  the  surface  of  the  mercury 
as  before,  and  reading  off  its  level.  The  instrument  is  then  held 
in  the  way  represented  in  the  figure,  the  thumb  firmly  closing  its 
aperture,  and  the  knuckle  of  the  forefinger  touching  the  nearer 
platinum  wire.  The  explosion  is  produced  by  the  aid  of  the 
electrophorus,  prime  conductor,  or  charged  jar,  as  before  de- 
scribed, the  violence  of  the  expansion  being  moderated  by  the 
spring-like  action  of  the  air  contained  in  the  open  limb.  The 
level  of  the  mercury  is  again  equalized  by  pouring  into  the  open 
side  enough  to  produce  that  result,  and  the  volume  of  the  gaseous 
mixture  is  then  finally  read  off. 

The  loss  in  volume  of  the  mixture,  which  is  produced  by  the 
explosion,  gives,  by  a  very  simple  process,  the  amount  of  oxygen 
originally  contained  in  the  air.  As  hydrogen  unites  with  oxy- 
gen to  form  water  in  the  proportion  by  measure  of  two  to  one, 
one-third  of  the  diminution  must  be  due  to  the  oxygen  of  the  air 
introduced.  Thus,  if  100  measures  of  air  and  50  of  hydrogen 


ELECTRICITY  DEVELOPED  BY  GALVANIC  ACTION.    547 

have  been  introduced,  and  if  the  mixture  contain  only  87  mea- 
sures after  explosion,  the  diminution  has  been  that  of  63  measures. 
One-third  of  the  loss  is  equal  to  21  measures,  which  represents 


duced  °f  the  air 

The  same  precautions  are  to  be  observed  in  manipulating  with 
this  instrument  as  directed  for  the  common  eudiometer. 

ELECTRICITY  DEVELOPED  BY  GALVANIC  ACTION.!  All  the 
foraw  of  apparatus  for  the  purpose  of  producing  a  continuous 
electrical  current,  are  called  galvanic  circuits,  and  those  in  com- 
mon use  consist  of  two  metals,  one  more  oxidable  than  the  other 
and  of  a  liquid,  which,  by  its  action  upon  the  readily  oxidized  or 
active  metal  causes  the  development  of  the  influence.     The  old 
voltaic  pile  and  the  crown  of  cups  are  the  most  simple  examples 
of  galvanic  apparatus.     The  former  consists  of  a  series  of  disks 
of  zinc  and  copper,  platinum  or  silver,  arranged  in  a  column, 
each  piece  of  different  metal  having  placed  between  it  and  its 
neighbor  a  disk  of  cloth,  or  paper,  steeped  in  some  liquid  which 
acts  chemically  upon  the  zinc.     The  crown  of  cups  is  differently 
arranged,  but  upon  the  same  principle.     A  number  of  cups  are 
placed  in  row  or  circle,  each  one  containing  an  exciting  liquid, 
such  as  dilute  sulphuric  acid,  and  a  plate  of  zinc,  and  one  of  the 
inactive  metal.     The  zinc  of  one  cup  is  connected  by  a  wire  with 
the  copper  or  other  metal  of  the  next  cup,  and  the  zinc  of  that 
is  also  connected  with  the  copper  of  the  one  beyond  it.     The  two 
external  plates  of  both  kinds  of  series  have  wires  soldered  to 
them,  which  are  called  the  poles.     In  this  way  a  communication 
exists  between  all  the  parts  of  the  series,  directly  between  the 
alternate  plates  of  the  different  cups,  and  indirectly  through  the 
liquid  between  those  in  the  same  cup.     A  simple  circuit,  as  exhi- 
bited by  the  most  elementary  form  of  either  of  these  arrange- 
ments, represents  in  miniature  all  the  other  kinds  of  voltaic  ap- 
paratus employed.     Thus,  if  a  single  cup  be  used,  containing  a 
plate  of  zinc  and  one  of  copper,  immersed  in  dilute  acid,  and 
having  wires  attached  to  them,  the  voltaic  current  is  supposed  to 
be  developed  upon  the  surface  of  the  zinc,  along  with  its  partial 
solution  and  the  evolution  of  hydrogen,  to  pass  through  the  liquid 
to  the  copper,  and  to  be  conducted  through  that  metal  to  the  end 
of  its  wire,  which  forms  the  anode  or  positive  pole.     The  end 


548          ELECTRICITY  DEVELOPED   BY  GALVANIC  ACTION. 

of  the  wire  attached  to  the  zinc  is  the  kathode  or  negative  pole. 
When  these  poles  are  placed  in  contact  with  each  other,  or  with 
a  conductor  of  the  fluid,  the  electricity  originally  developed  upon 
the  surface  of  the  zinc  returns  to  it  from  the  positive  wire  through 
the  negative  one ;  and  if  the  current  be  sufficiently  powerful,  the 
various  phenomena  of  voltaic  light,  heat,  electro-magnetism, 
chemical  decomposition  and  action  on  the  living  body,  are  capable 
of  being  exhibited  during  this  passage  from  pole  to  pole. 

In  most  of  the  forms  of  compound  circuits,  where  a  number  of 
pairs  of  plates  are  arranged  together  in  a  battery,  the  wire  at- 
tached to  the  terminal  zinc  plate  becomes  the  positive  pole,  and 
that  of  the  last  copper  plate  the  negative  one.  This  arises  from 
the  fact  that  in  these  arrangements  the  last  two  plates  are  actu- 
ally superfluous,  not  being  so  much  producers  of  the  galvanic 
fluid,  as  conductors  of  that  which  has  been  generated  in  the 
intermediate  parts  of  the  apparatus. 

The  more  oxidable  of  the  metals  should  form  a  readily  soluble 
salt  with  the  exciting  liquid.  If  both  'metals  are  easily  acted 
upon  by  the  liquid,  the  electrical  current  produced  by  one  will  be 
overcome  in  proportion  to  the  action  of  the  liquid  on  the  other. 
So  that  the  most  power  will  be  obtained  by  having  one  metal 
that  is  easily  acted  upon  and  another  that  will  remain  unchanged 
in  the  liquid.  The  metal  dissolved  is  always  the  positive  metal, 
and  the  unchanged  metal  the  negative  element.  Thus,  in  an 
acid  solution,  silver  is  positive  to  platina  and  negative  to  zinc. 

The  following  table  of  substances  shows  their  electrical  rela- 
tion to  each  other  in  sulphuric  acid,  commencing  with  the  most 
positive,  and  each  element  being  respectively  positive  and  nega- 
tive to  those  that  precede  and  follow  it. 

Potassium,  Bismuth, 

Barium,  Nickel, 

Zinc,  Silver, 

Cadmium,  Antimony, 

Tin,  Palladium, 

Iron,  Gold, 

Lead,  Charcoal, 

Copper,  Platinum. 

The  conducting  power  of  bodies  is  different.  Fluids  are  gene- 
rally imperfect  conductors ;  the  metals  and  carbon  are  the  best. 


WOLL ASTON *S   BATTERY.  549 

Some  of  the  metals  are  better  conductors  than  others;  the  relative 
conducting  power  of  eight  of  them,  is  as  follows : 


Silver,     ...  100 

Copper,   ...  100 

Gold,       .     'S-..    >;;.  67 

Zinc,        .         .         .  33 


Platinum,  ...  20 

Iron,          ...  20 

Tin,      Skate    .        .  17 

Lead,      ,*'•   '  .        .  10 


The  efficiency  of  a  battery,  as  regards  intensity  and  quantity, 
depends  upon  the  amount  of  surface  of  the  positive  metal  acted 
upon,  the  distance  between  the  positive  and  negative  elements, 
the  purity  of  the  materials,  the  size  and  length  of  the  connections, 
the  temperature  of  the  atmosphere,  and  the  good  condition  of  all 
the  parts  of  the  battery,  and  complete  connections. 

In  constructing  batteries,  only  the  purest  zinc  should  be  used ; 
and  especial  care  should  be  taken  to  prevent  its  contamination 
with  tin,  which  always  shows  itself  by  rising  in  flocculent  masses 
to  the  surface  of  the  solution. 

To  prevent  local  action  in  the  batteries,  which  is  occasioned  by 
impurities  in  the  zinc,  the  zinc  should  be  amalgamated  by  first 
dipping  it  in  chloro-hydric  or  sulphuric  acid,  and  then  quickly 
immersing  in  mercury,  of  which  they  should  be  made  to  absorb 
as  much  as  possible.  The  excess  of  mercury  is  removed  with  a 
cloth,  and  the  zinc  well  rinsed  with  water.  Two  and  one  quarter 
ounces  of  mercury  will  amalgamate  a  square  foot  of  zinc  surface. 
When  batteries  are  not  in  use,  all  the  parts  should  be  removed 
from  the  vessels  containing  the  liquids,  well  washed,  and  kept 
covered  from  the  dust. 

Wollaston's  Battery. — This  is  the  very  best  of  the  old  forms, 
of  the  voltaic  battery.  It  consists,  as  shown  in  Fig.  465,  of  a 
number  of  zinc  and  copper  plates,  the  latter  entirely  encircling 
the  former  except  at  the  edges,  and  the  two  metals  being  kept 
apart  by  pieces  of  cork  or  wood.  Each  plate  of  zinc  is  soldered 
to  the  one  of  copper  which  is  before  it  in  the  series,  and  the 
whole  arrangement  is  screwed  to  a  bar  of  dry  mahogany,  which 
permits  its  elevation  from  or  depression  into  the  acid.  This  is 
contained  in  an  earthenware  trough,  divided  by  partitions  into 
compartments,  each  one  of  which  receives  a  single  pair.  The 
exciting  liquid  is  made  of  a  mixture  of  100  parts  by  measure  of 
water,  2J  parts  of  sulphuric  acid,  and  2  parts  of  strong  nitric 
acid.  In  the  same  manner  that  the  shock  of  the  Leyden  jar  i% 


550  WOLLASTON'S  BATTERY. 

increased  by  combining  it  with  others  in  a  battery,  the  power  of 
this  apparatus  can  be  multiplied  to  any  desired  extent,  by  uniting 

Fig.  465. 


it  by  means  of  strips  of  copper,  passing  from  the  zinc  of  one 
instrument  to  the  copper  of  another,  with  any  desired  number  of 
similar  batteries. 

The  chief  objection  to  the  use  of  this  and  like  forms  of  appa- 
ratus is  what  is  called  the  local  action,  which,  in  it,  is  very  great, 
and  which  gives  rise  to  a  rapid  diminution  of  power  and  corrosion 
of  the  zinc. 

The  bubbles  of  hydrogen  given  off  from  its  surface,  adhere  to 
the  zinc,  preventing  perfect  contact  with  the  exciting  fluid  ;  some 
of  the  electricity  is  dissipated  by  the  escaping  gas,  and  the  sul- 
phate of  zinc  which  is  formed,  is  in  part  reduced  to  the  metallic 
state,  in  a  crust  upon  the  surface  of  the  copper.  All  of  these 
circumstances  form  serious  objections  to  the  use  of  this  battery 
where  a  long-continued  action  is  desired. 

When  common  zinc  is  exposed  to  dilute  sulphuric  acid,  it  is 
rapidly  dissolved,  and  this  solution  and  loss  of  material  in  the 
common  batteries  are  excessive  and  entirely  disproportional  to 
the  amount  of  galvanic  fluid  given  off.  This,  which  is  the  local 
action,  is  supposed  to  arise  from  a  number  of  little  voltaic  circles 
being  formed  by  the  presence  in  the  zinc  of  particles  of  plum- 
bago, and  of  other  metals  which  excite  the  rapid  erosion  of 
parts  of  its  surface.  This  evil  can  only  be  prevented,  as  before 
directed,  by  carefully  amalgamating  the  surfaces  of  the  zino 
plate. 


DANIELL'S  CONSTANT  BATTERY.  551 

A  single  pair  of  Wollaston's  battery  is  very  efficient  in  the 
production  of  the  phenomena  which  are  due  to  the  evolution  of  a 
quantity  of  electricity,  such  as  ignition  and  deflagration  on  a 
small  scale,  the  deflection  of  the  magnetic  needle,  and  the  various 
electro-magnetic  experiments.  Its  intensity  or  electro-chemical 
power  is  very  much  increased,  as  before  stated,  by  combining  it 
with  other  similar  arrangements. 

The  plates  of  the  old  form  of  voltaic  apparatus  should  be 
removed  from  the  acid,  and  washed  with  water  after  the  comple- 
tion of  each  experiment,  or  if  they  are  permanently  connected 
with  the  trough,  the  acid  in  it  should  be  poured  out,  and  reserved 
for  future  operations.  In  Wollaston's  battery,  the  plates  are 
taken  out  by  elevating  the  mahogany  bar  to  which  they  are  at- 
tached, and  freed  from  acid  and  metallic  deposit  by  washing  with 
water,  and  are  then  either  suspended  over  the  trough  by  a  cord 
attached  to  a  support  above,  or  are  placed  upon  a  tile  or  old  table 
until  their  next  employment.  As  the  acid  solution  soon  becomes 
unfit  for  use  from  the  large  amount  of  sulphate  of  zinc  dissolved 
in  it,  it  must  be  removed  after  reaching  a  certain  point  of  satu- 
ration. The  best  evidences  of  the  cleanliness  and  perfect  con- 
nection of  the  surfaces,  and  of  the  activity  of  the  liquor,  are 
afforded  by  the  constant  bubbling  up  of  hydrogen  during  the 
action,  and  by  the  ordinary  voltaic  phenomena  exhibited  at  the 
poles. 

Daniel? s  Constant  Battery. — This  is  a  far  better  form  of  ap- 
paratus than  the  one  last  described,  and  has  the  advantage  over 
it  of  being  comparatively  permanent  in  its 
action.  The  local  action  being  obviated  by  Flg<  466> 

the  amalgamation  of  the  zinc,  it  is  of  course 
much  more  applicable  to  those  purposes  of 
electro-chemical  examination  in  which  long 
continued  and  uniform  transmission  of  the 
fluid  through  a  body  is  desired.  In  its 
simplest  form,  it  consists  of  a  copper  cylinder 
A,  3  or  4  inches  in  diameter,  and  from  6  to 
18  inches  in  height,  containing  in  its  interior 
a  cell  of  porous  earthenware  or  of  animal  membrane,  within  which 
is  suspended  a  rod  of  zinc,  three-quarters  of  an  inch  in  diameter, 
which  has  been  carefully  amalgamated  by  rubbing  its  surface 


552  DANIELL'S  CONSTANT  BATTERY. 

with  mercury  by  means  of  a  cloth  previously  dipped  in  dilute 
sulphuric  acid.  The  earthen  cell  or  membrane  containing  the 
zinc  is  filled  with  a  mixture  of  one  part  by  measure  of  sulphuric 
acid  and  8  parts  of  water,  and  the  space  between  it  and  the  outer 
copper  cylinder  contains  a  saturated  solution  of  sulphate  of  cop* 
per,  the  surface  of  which  should  be  upon  the  same  level  as  that 
of  the  solution  within  the  cell.  The  solution  of  blue  vitriol  is 
prepared  by  pouring  boiling  water  over  an  excess  of  crystals  of 
the  salt,  and  stirring  constantly  until  it  is  saturated. 

To  this  solution,  a  little  sulphuric  acid,  never  amounting  to 
more  than  one-tenth  part  by  measure,  of  the  whole,  should  be 
added.  In  order  that  this  liquor  be  kept  concentrated,  a  little 
perforated  copper  shelf,  seen  in  the  figure,  is  usually  placed  upon 
the  inside  of  the  cylinder,  within  an  inch  or  two  of  the  top.  This 
is  intended  to  contain  a  supply  of  crystals  of  the  sulphate.  They 
are  placed  at  the  upper  part  of  the  liquid,  because  that  portion 
becomes  exhausted  first,  and  because  the  saturated  solution  of  the 
crystals  in  its  passage  downwards  diffuses  itself  equably.  In  the 
absence  of  the  shelf,  a  strong  bag  of  loose  texture,  or  a  network 
of  copper  wire  attached  to  the  top  of  the  cylinder,  may  be  used 
to  contain  the  crystals. 

Attached  to  each  metal  of  Daniell's  battery  is  a  binding-screw 
to  form  connections.  When  wires  are  held  in  each  of  these,  and 
a  communication  from  the  cylinder  to  the  rod  is  made,  a  power- 
ful current  is  produced.  In  the  figure,  the  extremity  of  z  repre- 
sents the  positive  pole,  and  that  of  x  the  negative  one.  In  this 
arrangement  there  is  no  evolution  of  hydrogen,  and  no  local 
action  upon  the  zinc  or  consequent  unnecessary  erosion  of  its 
surface.  The  interior  of  the  copper  cylinder  becomes  covered 
with  a  compact  deposit  of  metallic  copper,  from  the  decomposi- 
tion of  the  oxide  by  the  nascent  hydrogen. 

The  intensity  or  power  of  producing  electro-chemical  decom- 
positions of  this  battery,  may  be  much  increased  by  associating 
it  with  a  number  of  others.  Ten  pairs,  so  arranged  that  the 
inactive  metal  of  one  is  attached,  by  copper  wires  or  strips,  to  the 
active  metal  or  the  zinc  of  the  next,  make  a  most  powerful  com- 
pound circuit,  quite  sufficient  for  nearly  all  the  purposes  of  the 
chemist. 

Daniell's  battery  may  be  constructed  very  simply  and  cheaply, 


SMEE'S  BATTERY.  553 

by  immersing  in  a  tumbler  or  jar  containing  a  solution  of  sul- 
phate of  copper,  a  copper  plate  of  the  proper  size,  bent  into  the 
form  of  a  cylinder,  and  having  suspended  in  its  centre  upon  a 
piece  of  wood  supported  on  the  top  of  the  outer  vessel,  an  amal- 
gamated zinc  bar.  This  is  surrounded  by  a  piece  of  bladder  or 
of  the  intestine  of  an  animal,  tied  at  its  lower  part,  and  contain- 
ing the  acid  liquor.  Bags  of  very  firm  sail  cloth,  well  sewn, 
make  excellent  diaphragms,  and  resist  the  action  of  the  acid  for 
a  long  time.  Cylinders  made  by  cementing  coarse  strong  brown 
paper,  at  the  edges  and  bottom,  also  answer  perfectly  well.  The 
terminal  wires  may  be  soldered  upon  the  top  of  the  metals  with 
which  they  are  to  be  connected,  and  the  solution  of  sulphate  of 
copper  may  be  kept  saturated  by  the  means  before  spoken  of. 
Very  little  chemical  action  upon  the  surfaces  of  these  batteries 
goes  on  when  the  voltaic  circuit  is  not  completed ;  nevertheless  it 
is  proper  always  to  pour  out  the  contents  of  the  diaphragm  or  to 
disconnect  the  zinc  bar  after  each  use  of  them.  The  liquid  may 
be  kept  in  a  separate  vessel,  and  employed  in  future  experi- 
ments. The  solution  in  the  outer  cylinder  may  be  allowed  to 
remain. 

Smee's  Battery. — This  simple  and  powerful  apparatus  is  chiefly 
used  to  excite  the  precipitations  of  metals  in  the  electrotype  or 
galvano-plastic  processes.   As  commonly  con- 
structed and  shown  in  Fig.  467,  it  consists  of 
two  plates  of  amalgamated  zinc,  clamped  to 
a  piece  of  wood  by  means  of  a  bent  strip  of 
brass,   and  furnished  with  a  binding-screw. 
Between  the  plates  of  zinc  is  fixed  one  of 
platinized  silver,  connected  at  its  upper  end 
with  another  similar  screw.     The  silver  is 
covered  over  with  a  thin  layer  of  platinum, 
by  first  roughening  the  surface  with  strong 
nitric  acid,  and,  after  washing,  placing  it  in  a 
vessel  of  water  acidulated  with  sulphuric  acid,  to  which  a  little 
chloride  of  platinum  has  been  added.     A  porous  vessel  of  pipe- 
clay or  earthenware,  or  an  animal  membrane,  with  a  plate  of  zinc 
in  its  interior,  and  containing  dilute  sulphuric  acid,  is  then  im- 
mersed in  the  other  receptacle,  and   the  silver  and  zinc  are 
connected  together  by  a  wire.     The  platinum  precipitates  upon 


554  GROVES'S  BATTERY. 

the  silver  surface  as  a  dark  and  granular  but  closely  attached 
deposit. 

This  rough  surface  of  the  silver  plate,  presenting  myriads  of 
minute  conducting  points,  greatly  facilitates  the  evolution  of  hy- 
drogen. The  only  liquid  used  to  excite  this  battery  consists  of 
one  part  of  sulphuric  acid,  and  seven  of  water.  The  addition  of 
a  few  drops  of  nitric  acid  makes  it  act  with  greater  intensity, 
but  it  is  not  advisable  to  use  it  unless  the  silver  is  thoroughly 
covered  with  platinum. 

Another  form  of  this  battery  consists  of  a  glass  vessel  like  a 
tumbler,  on  which  rests  the  frame  which  supports  the  metallic 
plates.  As  in  the  other,  two  screw-caps  on  the  top  of  the  frame 
allow  the  attachment  of  wires  for  the  conveyance  of  the  current. 
One  of  these  is  connected  with  a  central  slip  of  platinum  foil,  on 
each  side  of  which  descend  amalgamated  zinc  plates,  connected 
above  with  the  other  screw.  Like  Daniell's  batteries,  a  series  of 
these  may  be  connected  together,  by  making  communication 
between  the  alternate  zinc  and  platinum  plates. 

Grroves's  Battery. — This  is  the  most  energetic  battery  known. 
Its  activity  is  very  great,  and  though  this  prevents  it  from  being 
so  well  adapted  for  galvanoplastic  operations,  it  is  the  one  gene- 
rally employed  for  the  development  of  magnetism,  and  is  in  com- 
mon use  in  the  magnetic  telegraph. 

Various  forms  of  this  arrangement  are  met  with,  but  in  the 
most  common  one,  a  strip  of  platinum  foil,  furnished  above  with 
a  screw-cap,  is  immersed  in  a  cylinder  of  porous  earthenware, 
filled  with  strong  and  pure  nitric  acid.  The  cylinder  is  sur- 
rounded by  another  one  of  amalgamated  zinc,  also  provided  with 
a  screw-cap,  standing  on  short  legs,  and  divided  by  a  longitudinal 
opening  in  one  side,  in  order  to  permit  the  acid  to  circulate 
freely  around  it.  It  is  placed  in  a  glass  jar  or  tumbler,  contain- 
ing one  part,  by  measure,  of  sulphuric  acid,  and  eight  of  water. 
When  the  circuit  is  completed  by  bringing  together  the  wires 
placed  in  the  screws,  the  hydrogen  from  the  decomposed  water 
in  the  outer  vessel  is  not  given  off  in  the  gaseous  state,  but  pass- 
ing through  the  diaphragm,  combines  with  some  of  the  oxygen 
of  the  nitric  acid,  reducing  it  to  nitric  oxide.  Some  of  this  dis- 
solves in  the  acid,  and  the  rest  escapes  in  the  form  of  dense  red 


BUNSEN'S  BATTERY. 


555 


fumes  of  nitrous  acid,  formed  by  its  combination  with  the  oxygen 
of  the  air. 

This  battery  owes  its  intensity  and  rapidity  of  action  to  the 
absorption  of  the  hydrogen,  the  good  conducting  nature  of  the 
materials,  and  the  consequent  concentration  of  the  fluid.  It  has 
been  said  to  be,  when  properly  prepared,  about  seventeen  times 
more  powerful  than  that  of  Daniell.  The  great  objection  to  its 
use  arises  from  the  escape  of  the  irritating  and  poisonous  nitrous 
acid,  which  is  sometimes  so  considerable  as  to  fill  the  apartment 
with  the  fumes. 

Bunsen's  Battery. — This  is  the  same  in  principle  as  Groves's 
battery,  but  is  more  economical,  as  a  cylinder  of  porous  coal  is 
used  in  place  of  platinum.  It  is  represented  in  Fig.  468.  A  B 

Fig.  468. 


Fig.  469. 


is  a  glass  vessel  filled  up  to  B'  B'  with  commercial  nitric  acid,  c 
and  c'  are  hollow  charcoal  cylinders,  dipping  into  the  acid  as  far 
as  B"  B",  and  resting  on  the  edge  of  the  glass  by  a  flange.  A 
ring  of  zinc  or  copper  P  encircles  the  top  of  the  charcoal  cylin- 
der, and  terminates  in  an  appendage  P',  for 
connecting  it  with  the  wire.  D  D,  which  are 
diaphragms  of  porous  earthenware,  contain 
an  amalgamated  hollow  zinc  cylinder  z  z,  with 
its  appendage  P",  also  intended  for  communi- 
cation, and  which  is  immersed  in  dilute  sul- 
phuric acid.  The  connections  are  made  by 
means  of  the  clamp  A  B,  Fig.  469,  and  screw  v,  which  are  shown 
in  place  at  H,  Fig.  468.  The  perfect  contact  of  these  appen- 


556  CONNECTION  OF  BATTERIES. 

dages,  screws,  and  the  ribbons  or  wires  of  copper  connected  with 
them,  must  be  secured,  by  keeping  them  clean  and  bright  by 
rubbing  with  sand  paper.  When  the  battery  is  about  to  be  used, 
the  glass  vessel  is  half  filled  with  equal  parts  of  commercial  nitric 
acid  and  water,  and  the  diaphragm  with  water  acidulated  with 
sulphuric  acid.  The  coal  cylinder  is  prepared  by  pressing  a 
thorough  mixture  of  one  part  of  caking  coal  and  two  of  coke  with 
a  little  rye  flour,  into  a  cylindrical  mould  of  sheet-iron,  in  the 
centre  of  which  is  a  core  of  wood  or  pasteboard.  The  mould, 
after  being  closed  by  a  movable  cover  well  luted  on,  is  heated 
gradually  to  redness,  and  the  calcination  is  continued  until  the 
disengagement  of  gas  ceases.  The  cylinder  is  then  taken  out, 
soaked  in  a  strong  solution  of  molasses,  dried,  and  again  cal- 
cined by  an  intense  heat,  in  order  to  increase  its  firmness  of  tex- 
ture. After  this,  its  surface  may  be  smoothed  off  with  a  file,  or 
in  a  lathe.  ; 

This  battery  is  said  to  be  almost  equal  to  Groves's  in  power. 
Professor  Bird  has  constructed  one  similar  to  it  by  the  use  of  a 
black  lead  crucible.  He  ignited  the  crucible  for  a  short  time, 
and,  when  thus  prepared,  filled  it  with  nitric  acid,  and  wound  a 
wire  tightly  around  its  outside,  making  it  serve  both  as  a  support 
and  as  the  conductor  of  the  fluid.  A  bar  of  amalgamated  zinc, 
also  connected  with  a  wire,  was  then  placed  in  a  porous  cylin- 
der containing  dilute  sulphuric  acid,  and  the  whole  was  immersed 
in  the  acid  of  the  crucible.  He  states  that,  although  powerful, 
it  is  much  inferior  to  Groves's  battery. 

In  the  use  of  any  of  the  above-described  batteries,  care  must 
be  taken  not  to  fill  either  of  the  receptacles  too  full  of  the  liquid, 
since  on  immersing  the  metals  or  charcoal,  some  part  of  it  might 
overflow  and  mix  with  that  of  the  other  vessel,  to  the  injury  of 
the  surfaces.  After  the  insertion  of  the  cylinders  or  bars,  the 
surfaces  of  the  two  liquids  must  be  as  nearly  as  possible  upon  the 
same  level ;  any  deficiency  in  this  respect  must  be  regulated  by 
the  addition  of  more  fluid. 

Connection  of  Batteries. — The  connection  between  the  dif- 
ferent plates  of  batteries  is  very  conveniently  made  by  means  of 
the  binding-screw,  Fig.  470.  The  wire  by  which  the  communi- 
cation is  established  is  passed  through  the  hole  in  the  side,  and 
kept  in  its  place  by  the  movable  screw  in  the  top.  The  screw 


WIRE  FQE  BATTERY  PURPOSES. 


557 


below  serves  to  fasten  the  arrangement  firmly  into  a  hole  of  the 
proper  size,  in  the  top  of  either  plate.  The  operator  should  be 
supplied  with  a  number  of  these,  as  they  permit  him  to  unite  and 

Fig.  470. 


disconnect  the  different  parts  of  an  apparatus  with  the  greatest 
ease  and  rapidity.  They  are  shown  in  the  figure,  attached  to  the 
copper  and  zinc  plates  of  a  simple  circuit,  with  the  wires,  of  which 
the  ends  form  the  poles,  passing  through  them. 

Wire  for  Battery  Purposes. — Copper  wire  is  more  often  em- 
ployed for  connecting  the  different  parts  of  a  voltaic  circuit  than 
any  other,  on  account  of  its  high  conducting  power,  its  flexibility, 
and  its  not  being  susceptible  of  magnetization  by  the  passage 
through  or  around  it  of  a  galvanic  current.  Its  thickness  should 
be  proportioned  to  the  energy  of  the  battery,  and  it  should  be  as 
short  as  possible,  because  a  great  length  of  wire  causes  resistance 
to,  and  loss  of  the  fluid  proceeding  from  a  battery  of  moderate 
power.  Its  connecting  parts,  as  well  as  those  of  the  plates  or 
screws  to  which  it  is  attached,  must  be  bright  and  clean.  In 
order  to  insure  perfect  contact,  it  is  advisable  to  amalgamate  the 
extremities  of  the  wire ;  which  is  done  by  washing  them  with  a 
solution  of  nitrate  of  mercury,  and  dipping  them  afterwards  in 
metallic  mercury. 

When  it  is  desired  to  break  and  renew  the  connections  often  or 
very  rapidly,  the  common  mode  of  attaching  the  wires  is  found 
to  be  inconvenient.  In  that  case,  a  little  cup  made  of  copper,  or 
other  metal  which  does  not  too  readily  amalgamate  with  mercury, 
is  partly  filled  with  that  metal,  and  the  wires  are  received  in  the 
cup,  a  depression  in  the  bottom  of  the  latter  being  often  made  so 
as  to  hold  them  more  firmly  in  their  place.  By  keeping  one  of 
the  wires  immersed  in  this  cup,  the  connection  may  be  made 


558  ELECTROLYSIS. 

complete  or  broken  at  will,  and  without  disarranging  any  part  of 
the  apparatus,  by  simply  placing  the  extremity  of  the  other  wire 
in  its  appropriate  cup,  or  taking  it  out. 

The  wires  are,  in  one  point  of  view,  the  most  interesting  parts 
of  the  battery,  as  it  is  at  their  extremities,  or  the  electrodes,  that 
the  most  important  phenomena  of  galvanism  are  exhibited.  Their 
size  and  length  should  be  adapted  to  the  power  of  the  battery. 

Electrolysis. — Any  one  of  the  batteries  already  mentioned  may 
be  employed  for  the  purpose  of  producing  chemical  decomposi- 
tions, by  passing  the  current  from  them  through  the  substance, 
from  pole  to  pole,  of  the  terminal  wires  of  the  series.  As  electro- 
chemical changes  are  usually  effected  most  perfectly  by  a  current 
of  intensity,  as  distinguished  from  one  of  quantity,  which  is  more 
active  in  producing  light,  heat,  and  electro-magnetism,  a  number 
of  pairs  of  plates  or  cylinders,  varying  with  the  difficulty  of  the 
decomposition,  are  employed.  The  other  results  spoken  of  are 
generally  obtained  by  using  a  small  number  of  plates  with  large 
surfaces.  A  combination  of  small  batteries,  made  upon  the  plan 
of  Daniell's,  is,  perhaps,  the  most  active  of  all  in  producing 
chemical  change. 

Whatever  form  of  apparatus  is  used  for  such  decompositions, 
particular  attention  must  be  paid  to  the  proper  connection  of  the 
alternate  metals,  and  to  the  close  contact  of  the  wires,  as  well  as 
the  other  circumstances  before  spoken  of  in  reference  to  their 
relative  size.  The  points  of  the  wires  should,  in  most  cases,  be 
made  of  platinum,  as  that  metal  is  the  best  conductor  of  the  fluid, 
and  is  not  liable  to  be  chemically  acted  on  by  any  of  the  sub- 
stances evolved  from  the  electrolyte. 

Any  one  of  the  class  of  bodies  called  electrolytes,  which  includes 
all  those  known  to  be  capable  of  decomposition  by  electricity, 
may  be  exposed  to  the  voltaic  influence  by  being  placed  between 
the  electrodes  or  extremities  of  the  wires,  so  as  to  be  the  medium 
of  communication  between  them.  This  is  effected  in  various  ways, 
as  the  substances  differ  in  being  solid  or  fluid,  and  good  or  bad 
conductors  of  the  influence. 

Many  solutions,  like  that  of  iodide  of  potassium,  admit  very 
readily  of  decomposition.  A  solution  of  this  salt  may  be  easily 
decomposed  by  a  battery  consisting  only  of  a  wire  of  zinc  and 
one  of  copper.  Water  alone,  however,  may  require  the  power  of 


ELECTEOLYSIS.  559 

a  number  of  cells  of  Darnell's  battery  to  separate  it  into  its  ele- 
ments. The  addition  of  a  little  common  salt,  or  of  almost  any 
saline  body,  will  make  the  electrolysis  of  it  much  more  easy  by 
increasing  its  conducting  power. 

In  the  decomposition  of  water,  and,  indeed,  in  most  cases  in 
which  gaseous  components  of  bodies  are  eliminated  from  liquids, 
platinum  strips  are  attached  to  the  ends  of  the  wires,  thus  making 
the  surfaces  of  contact  much  greater.  These  strips,  which  may 
be  made  of  platinum  foil,  are  placed  parallel  and  as  close  to  each 
other  as  is  possible,  without  their  being  actually  in  contact. 
Their  touching  each  other  would  effectually  prevent  all  chemical 
action,  as  the  voltaic  fluid  would  be  directly  transmitted  through 
the  wires  from  the  positive  to  the  negative  plates. 

When  the  electrodes  are  placed  in  a  vessel  of  water,  and  the 
battery  is  made  to  act  properly,  bubbles  of  hydrogen  will  ascend 
from  the  end  of  the  wire  or  foil  connected  with  the  negative  end, 
and  oxygen  from  that  of  the  positive  one.  These  gases  can  be 
collected  in  a  tube  closed  at  one  end,  or  a  jar  previously  filled 
with  water,  and  inverted  over  the  wires ;  or  they  may  be  sepa- 
rately received  in  different  vessels.  As  water  consists  of  two 
volumes  of  hydrogen  and  one  of  oxygen,  of  course  the  quantity 
of  the  first  given  off,  will  be  twice  that  of  the  last.  Fig.  471  re- 
Fig.  471. 


presents  a  mode  of  effecting  this  decomposition  in  which  the 
terminal  wires  of  a  trough  arrangement  are  passed  through  a 
perforated  cork  into  water  contained  in  a  funnel.  The  end  of 
each  wire  is  placed  directly  under  a  test-tube  previously  filled 
with  water,  and  inverted  in  the  funnel.  The  ascending  gases 


560  ELECTROLYSIS. 

displace  the  water,  occupy  the  tube,  and  may,  if  necessary,  be 
accurately  measured. 

As  the  quantity  of  electricity  set  in  motion  by  the  battery  is 
in  direct  proportion  to  the  amount  of  zinc  dissolved  in  it,  so  are 
the  effects  of  chemical  decomposition  always  proportionate  to  the 
former;  this  being  thus  always  in  a  certain  relation  with  the 
equivalents  both  of  the  products  of  electrolysis  and  of  the  portion 
of  zinc  acted  upon.  Thus,  one  grain  of  hydrogen,  given  off  at 
the  negative  pole,  indicates  that  thirty-three  grains  of  zinc  have 
been  dissolved  during  the  time  of  the  action.  Upon  this  prin- 
ciple Faraday  constructed  his  voltameter,  which  affords  the  only 
means  known  of  accurately  measuring  the  galvanic  influence. 
That  form  of  this  which  is  most  employed,  is  one  in  which  strips 
of  platinum  foil,  attached  to  the  wires  of  a  battery,  are  placed 
opposite  and  near  to  each  other  in  a  jar.  or  bottle,  from  which  a 
tube  issuing,  enters  under  a  graduated  jar  inverted  over  the 
pneumatic  trough,  all  of  these  vessels  being  full  of  water.  By 
the  measure  of  the  gases  collected,  the  quantity  of  electric  force 
can  be  estimated.  By  placing  strips  of  platinum  upon  the  ends 
of  the  wires  in  Fig.  471,  and  substituting  a  single  graduated  tube 
with  a  wide  or  funnel-shaped  mouth,  for  the  two  which  are  seen 
in  the  cut,  the  same  result  may  be  attained. 

Faraday  describes  a  convenient  form  of  tube  for  the  collection 
and  examination  of  gases  evolved  from  either  electrode,  in  expe- 
F.  4?2  riments  conducted  upon  a  small  scale.  This  tube, 
represented  in  Fig.  472,  is  filled  with  the  solution 
to  be  acted  upon,  and  held  in  the  position  repre- 
sented. The  nature  of  the  gas  to  be  collected, 
depends  on  the  end  of  the  battery,  which  is  fastened 
to  the  curved  wire  at  a.  The  other  electrode  is 
to  be  loosely  inserted  at  b,  so  as  to  allow  the  gas 
given  off  from  it,  to  escape  through  the  open  orifice. 
It  should  not  be  placed  so  far  within  the  extremity 
of  the  tube  as  to  permit  any  bubbles  of  the  gas  to  pass  around 
the  bend,  and  to  mix  with  that  in  the  upright  limb.  The  wire  b 
is  to  be  removed  when  a  sufficient  amount  of  gas  has  been  col- 
lected, and  the  latter  can  then  be  transferred  to  a  suitable  vessel 
and  examined. 

The  methods  of  subjecting  substances  to  the  action  of  the  bat- 


HEAT  AND   LIGHT  FROM   GALVANISM.  561 

tery  are  very  numerous.  "When  the  electrolyte  is  a  fluid,  it  may 
be  placed  in  any  one  of  a  great  variety  of  suitable  receptacles. 
In  all  cases  it  must  be  recollected  that  the  electrodes  should  be 
brought  as  near  together  as  possible,  so  that  the  small  amount  of 
the  substance  which  is  directly  between  them,  shall  have  the  full 
effect  of  the  current  concentrated  upon  it.  Decompositions  of  a 
drop  of  fluid  may  be  made  by  placing  it  upon  a  glass  plate,  and 
bringing  the  poles  in  contact  with  its  sides.  Larger  quantities 
may  be  received  in  a  watch-glass  or  other  concave  piece  of  glass, 
or  in  a  cup  of  the  proper  size.  A  very  convenient  mode  of  sub- 
jecting liquids  to  the  current,  so  that  the  results  of  the  decompo- 
sition can  be  easily  inspected  by  the  observer,  is  that  of  closing 
one  end  of  a  piece  of  glass  tube  tightly  with  a  cork,  and  support- 
ing it  in  an  upright  position  by  passing  one  of  the  wires  of  the 
battery  perpendicularly  through  the  cork.  The  tube  may  then 
be  filled  with  the  liquid,  and  the  other  wire,  bent  downwards, 
may  be  immersed  in  it,  and  placed  alongside  of  its  fellow.  In 
nearly  all  such  decompositions,  the  ends  of  the  poles  should  be 
armed  with  strips  of  platinum  foil,  on  account  of  the  greater 
surfaces  of  contact  presented  by  them. 

When  it  is  desired  to  direct  the  electrolytic  influence  upon  a 
large  surface  of  a  liquid,  a  piece  of  platinum  foil  attached  to  one 
pole  may  be  hollowed  out  into  a  cup-like  form,  and  the  substance 
may  be  placed  in  it ;  or  the  terminal  wire  may  be  made  to  support 
and  communicate  with  a  platinum  crucible,  by  being  wound  around 
it.  The  other  wire  can  then  be  immersed  in  the  liquid,  and  pre- 
vented from  touching  the  vessel  by  the  intervention  of  a  piece  of 
glass  tube. 

Production  of  Heat  and  Light  by  Galvanism. — The  physical 
effects  of  galvanism,  among  which  are  the  production  of  heat  and 
light,  result  generally  from  the  passage  of  a  current  of  great 
quantity  and  of  feeble  intensity,  through  an  insufficient  and  im- 
perfect conductor,  the  resistance  of  the  latter  impeding  the  cur- 
rent, and  increasing  its  calorific  power.  The  batteries  employed 
for  fusion  and  deflagration  generally  consist  of  a  very  small 
number  of  pairs  with  extensive  surfaces,  which  will  develop  a 
great  quantity  of  electricity.  Usually  these  are  the  best  batteries 
for  physical  experiments,  but  occasionally  those  consisting  of  a 
large  number  of  plates  are  found  useful  for  such  purposes.  A 

3G 


562  HEAT   AND   LIGHT   FROM   GALVANISM. 

single  pair  of  very  moderate  size  will  effect  these  results  in  a  small 
way.  Thus,  Dr.  Wollaston  fused  a  very  fine  wire  of  platinum  by 
means  of  a  small  battery,  made  of  a  lady's  thimble  and  a  rod  of 
zinc.  We  have  before  stated  that  the  intensity  or  decomposing 
power  of  the  galvanic  fluid  is  increased  by  placing  batteries  in 
connection  so  as  to  multiply  the  number  of  plates.  Batteries 
may  also  be  associated  together  so  as  to  increase  their  calorific 
and  light-producing  power.  Any  number  of  troughs  like  Wollas- 
ton's  may,  for  this  purpose,  be  placed, — not  as  before,  end  to 
end, — but  sidewise,  and  the  cells  at  either  end  of  each  may  be 
connected  with  the  same  cells  of  the  others  by  two  wires  going 
across  the  series,  and  so  bent  as  to  be  in  perfect  contact  with  the 
last  plates.  The  projecting  ends  of  these  wires  on  one  side  are 
to  be  used  as  the  poles  of  the  battery. 

Daniell's,  or  any  other  of  the  cell  batteries,  can  be  made 
capable  of  producing  the  physical  phenomena  of  electricity,  by 
paying  attention  to  the  size  and  conducting  power  of  the  wires  or 
other  bodies  to  be  heated ;  but  the  quantity  of  the  fluid  is  much 
increased  by  connecting  a  number  of  them  so  as  to  make  them 
equivalent  to  a  single  pair.  This  can  be  done  by  connecting 
together  all  the  copper  or  platinum  plates  by  means  of  wires, 
either  soldered  to  them  or  inserted  into  the  binding-screws  already 
spoken  of.  The  zinc  bars  or  cylinders  are  to  be  brought  into 
contact  in  like  manner,  and  the  poles  may  be  made  by  attaching 
wires  to  any  two  of  the  opposite  pieces  of  metal. 

The  wires  of  such  batteries  should  all  be  made  of  larger  size 
than  those  which  are  employed  in  the  ordinary  arrangements. 

When  the  electricity  developed  in  a  powerful  battery  is  passed 
through  conical  pieces  of  charcoal  placed  upon  its  poles,  and 
these  are  brought  into  contact,  and  then  withdrawn  to  a  short 
distance  from  each  other,  the  interval  becomes  occupied  with  a 
brilliant  spark  or  arch  of  flame,  the  light  of  which  is  often  too 
vivid  to  be  borne  by  the  eyes.  The  heat  given  out  is  also  very 
intense,  and  gases  and  other  bodies  are  sometimes  subjected  to 
its  influence  for  the  purpose  of  being  decomposed.  Carburetted 
and  sulphuretted  hydrogen  are  both  thus  affected  by  it.  The 
wires  may  be  twisted  around  two  pieces  of  fine,  well-burnt  char- 
coal, which  are  then  brought  together.  The  brilliancy  of  the 
spark  or  arch  passing  between  the  points  of  charcoal,  serves  often 


HARE'S  SLIDING-ROD  EUDIOMETER.  563 

to  indicate  the  power  and  good  condition  of  the  battery.  When 
a  very  powerful  current  is  set  in  motion,  it  is  advisable  not  to 
make  the  contact  by  means  of  the  hands,  but  to  use  insulated  dis- 
chargers analogous  to  those  employed  in  electrical  experimer-ts. 
The  wires  may  be  brought  together  and  disconnected  by  means 
of  clamps  or  small  vices  attached  to  wooden  handles.  These 
may  be  screwed  on  and  taken  off  at  pleasure.  The  charcoal  used 
in  these  experiments  must  be  of  the  best  quality.  It  is  properly 
prepared  by  packing  pieces  of  box  or  other  suitable  wood,  two 
inches  long,  and  a  quarter  of  an  inch  thick,  in  an  earthenware 
crucible,  and  after  covering  them  up  with  dry  sand,  heating  them 
until  they  cease  to  flame.  The  best  pieces  must  be  selected  and 
preserved  for  use  in  a  well-stoppered  vessel. 

Various  substances  ignite  and  burn  with  brilliancy  between  the 
galvanic  poles.  Metallic  leaves  or  foil  of  different  kinds  may  be 
conveniently  burned  by  taking  them  up  upon  the  point  of  one 
electrode,  and  bringing  them  in  contact  with  a  plate  of  polished 
tinned  iron,  which  is  attached  to  the  other.  In  this  way  the 
different  appearances  and  colors  of  their  flames  are  shown. 

A  platinum  wire  stretched  between  the  poles  of  a  battery,  will 
attain  a  red  or  white  heat,  and,  if  offering  sufficient  resistance  to 
the  passage  of  the  fluid,  may  even  be  fused.  It  must  not  be  too 
thin,  as  the  electricity  may  be  sometimes  so  much  retarded  as  to 
produce  no  visible  indications  of  heat.  A  wire  of  the  proper  size 
will  often  remain  at  a  red  heat  for  a  great  length  of  time  if  a 
constant  battery  is  used. 

The  power  possessed  by  the  battery  of  igniting  platinum  wire, 
enables  us  to  apply  heat  in  situations  in  which  it  would  be  diffi- 
cult or  impossible  to  do  it  by  other  means.  By  its  use,  substances 
placed  under  water  may  be  ignited  or  exploded,  if  necessary,  at 
a  great  distance  from  the  operator.  Out  of  the  laboratory,  it 
may  be  employed  for  the  purpose  of  exploding  gunpowder  in 
mines,  or  under  ships,  and  in  other  positions  far  removed  from 
the  source  of  electricity:  while,  in  it,  it  may  be  used  for  the  ex- 
plosive decomposition  of  various  gases. 

Dr.  Hare  has  taken  advantage  of  this  power  in  the  construc- 
tion of  his  sliding-rod,  aqueous,  eudiometer.  This  instrument 
consists  of  a  glass  vessel,  with  a  capillary  orifice  closed  by  a 
spring  and  lever  in  its  top,  and  connected  below  with  a  socket, 


564  HARE'S  CALORIMOTOR. 

and  a  tube  in  which  a  graduated  piston  moves.  A  fine  wire  of 
platinum  is  stretched  across  the  middle  of  the  vessel,  between  two 
brass  wires,  which  pass  through  the  socket  below,  and  terminate 
in  legs,  which  are  made  capable  of  connection  with  the  cups  upon 
the  poles  of  a  battery.  The  instrument  having  been  filled  with 
water,  the  gaseous  mixture  is  drawn  into  it  in  the  proper  quan- 
tities by  pulling  out  the  piston  to  regulated  distances,  and  is  then 
exploded  by  the  ignition  of  the  wire,  after  the  capillary  orifice 
has  been  closed.  This  last  is  now  again  opened,  but  under  water, 
enough  of  which  enters  to  supply  the  vacuum  produced  by  the 
condensation.  The  amount  of  undecomposed  air  which  remains, 
is  indicated  by  the  distance  through  which  the  rod  has  to  be 
passed  for  the  purpose  of  expelling  it  all  from  the  glass  vessel. 

Dr.  Hare  uses  for  the  ignition  of  the  wire  in  this  experiment, 
his  calorimotor  of  two  pairs  of  plates.  He  has  constructed  a 
variety  of  arrangements  for  procuring  the  heating  effects  of  the 
battery.  In  one  of  these,  twenty  sheets  of  copper,  and  the  same 
number  of  zinc  plates,  united  separately  to  two  bars  of  metal, 
were  secured  in  a  wooden  frame,  so  as  to  leave  a  space  between 
them  of  a  quarter  of  an  inch.  A  rope,  passing  over  a  pulley,  was 
attached  at  one  end  to  the  frame,  and  at  the  other  to  a  counterpois- 
ing weight.  The  frame  could  be  lowered  by  means  of  the  rope  into 
a  cubical  box  containing  the  acid  liquor.  Another  form  of  Hare's 
battery  is  so  constructed  that  the  vessel  containing  the  acid  is 
raised  up  to  and  lowered  from  the  plates,  when  necessary,  by 
means  of  a  lever  connected  with  pulleys.  By  this  most  conve- 
nient and  powerful  battery,  constructed  with  a  new  arrangement 
of  the  plates,  the  most  intense  galvano-ignition  and  deflagration 
may  be  accomplished. 

This  apparatus,  the  description  of  which  might,  perhaps,  have 
been  more  properly  introduced  along  with  the  account  of  other 
batteries,  is  shown  in  Figs.  473  and  474.  We  extract  the  de- 
scription of  it  from  Hare's  Compendium. 

"  The  two  forms  of  calorimotor,  represented  in  Figs.  473  and 
474,  have  been  much  used  by  me  for  what  is  described  in  my 
Compendium  as  'galvano-ignition.'  (C,  335.)  Within  any 
cavity,  ignition  of  any  intensity  short  of  fusing  platinum  may  be 
produced,  by  making  a  platinum  wire  the  subject  of  a  galvanic 
discharge  from  an  instrument  of  this  kind.  I  first  resorted  to  this 


HARE  S  CALORIMOTOR. 


565 


process  in  the  year  1820,  for  the  purpose  of  igniting  gaseous 
mixtures  in  eudiometers  of  various  forms.  In  June,  1831,  I 
applied  it  to  ignite  gunpowder  in  rock  blasting ;  and  to  this  object 
it  was  subsequently  applied,  agreeably  to  my  recommendation, 
by  Colonel  Pasley,  Professor  O'Shognessy,  and  others. 

Fig.  473. 


"  This  machine  consists  of  sixteen  plates  of  zinc,  and  twenty 
plates  of  copper,  each  twelve  inches  by  seven,  arranged  in  four 
galvanic  pairs.  The  plates  are  supported  within  a  box  with  a 
central  partition  of  wood  A  B,  dividing  it  into  two  compartments. 
Each  of  these  may  be  considered  as  separated  into  two  subdivi- 
sions, by  four  plates  of  copper  between  the  letters  c  c.  Of  course 
the  box  may  be  considered  as  comprising  four  distinct  spaces,  No. 
1,  No.  2,  No.  3,  and  No.  4.  The  circuit  is  established  in  the 
following  manner.  Between  the  zinc  plates  of  compartment  No, 


566  ELECTRO-METALLURGY. 

1,  and  the  copper  plates  of  compartment  No.  2,  a  metallic  com- 
munication is  produced  by  soldering  their  neighboring  corners 
to  a  common  mass  of  solder,  with  which  a  groove  in  the  wooden 
partition  between  them  is  filled.  With  similar  masses  of  solder, 
two  grooves  severally  made  in  the  upper  edges  of  each  end  of  the 
box  are  supplied.  To  one  of  them,  the  corners  of  all  the  copper 
plates  of  space  No.  1  and  the  zinc  of  space  No.  4,  are  soldered. 
To  the  other,  the  zinc  plates  of  space  No.  2  and  the  copper 
plates  of  space  No.  3,  are  soldered  in  like  manner.  Lastly,  the 
zinc  plates  of  No.  3  are  connected  by  solder  in  a  groove,  and  the 
copper  plates  of  No.  4  are  in  like  manner  connected  by  solder  in 
another  groove.  Upon  the  ends  s  s  of  the  solder  just  mentioned, 
the  gallows-screws  are  severally  soldered,  and  to  these  the  rods 
p  P,  called  poles,  are  fastened.  The  means  by  which  the  acid  is 
made  to  act  upon  the  plates  must  be  sufficiently  evident  from  in- 
spection. Depressing  the  handle  causes  the  wheels  to  revolve, 
and  thus,  by  means  of  the  cord  which  works  in  their  grooved 
circumferences,  to  lift  the  receptacle  which  holds  the  acid,  until 
this  occupies  interstices  between  the  plates." 

ELECTRO-METALLURGY. — The  deposition  of  metals  by  electric 
action  is  one  of  the  modern  triumphs  of  practical  chemistry.  The 
art  dawned  in  1805  with  the  discoveries  of  Brugnatelli ;  but  no 
substantial  benefits  were  derived  from  it  until  1838,  when  Jacobi, 
of  St.  Petersburg,  and  Spencer,  of  England,  applied  the  prin- 
ciple to  the  utilitarian  purposes  of  life.  The  subsequent  inven- 
tion, by  Daniell,  of  his  well-known  battery  gave  an  impulse  to 
the  art  which  resulted  in  many  gratifying  and  wonderful  improve- 
ments ;  so  that  now  it  has  become,  in  its  greatly  advanced  con- 
dition, a  prime  element  of  the  economy  of  many  branches  of 
manufacture.  Plating,  gilding,  stereotyping,  medal  copying, 
engraving,  and  kindred  arts,  are  all  largely  indebted  to  electro- 
metallurgy for  many  of  the  facilities  which  at  present  promote 
and  distinguish  their  progress. 

Those  who  may  wish  to  experiment  in  this  interesting  branch 
of  scientific  art  will  find  ample  instruction  in  the  following  pages. 

Any  of  the  many  forms  of  batteries  previously  described  may 
be  used  for  electrotyping,  but  the  best  is  Srnee's.  Care  should 
be  taken  to  observe  the  directions  heretofore  given  for  the  treat- 


MOULDS.  567 

ment  and  management  of  batteries ;  their  good  condition,  proper 
arrangement  and  management,  being  necessary  to  success. 

The  intensity  and  quantity  of  the  galvanic  current  should  be 
proportional  to  the  work  to  be  done. 

Preparation  of  Articles  to  be  Plated  or  Copied. — In  gilding 
and  silvering,  it  is  merely  necessary  to  have  the  objects  perfectly 
clean  and  bright.  This  is  effected  by  first  boiling  the  articles  in 
a  solution  of  caustic  soda  or  potassa,  and  afterwards  immersing 
them  in  dilute  nitric  acid,  and  rinsing  with  water.  They  are 
further  cleaned  by  rubbing  with  a  hard  brush,  and  sometimes  a 
little  fine  sand  or  tripoli. 

Moulds.  —  Many  substances  are  used  for  making  moulds; 
among  the  best  are  beeswax,  plaster  of  Paris,  fusible  metal,  and 
gutta  percha. 

Wax  moulds  are  prepared  by  melting  the  wax  over  a  water- 
bath,  and  stirring  in  one  ounce  of  white  lead  to  each  pound  of 
•wax.  The  wax  should  be  clear  and  free  from  impurities. 

If  the  object  to  be  copied  is  a  medal,  it  should  be  brushed  over 
•with  sweet  oil,  and  the  excess  of  oil  removed  with  a  cloth.  A 
slip  of  metal  or  card  is  bound  round  the  edges  of  the  medal,  so 
as  to  form  a  rim.  The  wax  being  melted,  the  medal,  to  prevent 
air-bubbles,  is  held  in  an  inclined  position,  and  the  wax,  which 
should  not  be  too  hot,  poured  gently  on  the  lowest  part,  and 
allowed  gradually  to  spread  over  the  surface  of  the  medal  by 
bringing  it  to  a  level  when  it  is  filled  to  the  top  of  the  rim  with 
wax.  As  soon  as  the  wax  begins  to  set,  the  band  should  be  re- 
moved to  prevent  cracking.  Let  the  medal  and  wax  remain 
together  until  entirely  cold,  so  that  they  may  be  easily  separated. 

If  it  is  desired  to  take  a  wax  mould  from  a  plaster-cast  or 
medallion,  a  similar  course  is  followed,  the  medallion  being  first 
prepared  as  follows:  the  medallion  is  warmed  a  little,  brushed 
over  with  boiled  linseed  oil,  and  allowed  to  dry  perfectly.  It 
then  presents  a  polished  appearance  and  is  ready  for  the  wax. 

Instead  of  oil,  water  is  often  used ;  the  plaster  being  saturated 
with  it  by  placing  the  back  of  the  medallion  in  the  water,  care 
being  taken  not  to  allow  the  water  to  flow  over  the  face  of  the 
medallion. 

Plaster  of  Paris  moulds  are  made  by  mixing  the  finest  calcined 
plaster  with  water,  to  form  a  thin  paste  about  the  consistence  of 


568  NON-CONDUCTING   SUBSTANCES. 

cream.  A  little  of  this  paste  is  poured  upon  the  object  and  well 
brushed  into  every  part  with  a  camel's  hair  brush,  and  then  more 
of  the  paste  is  added  to  produce  the  requisite  thickness.  It  is 
allowed  to  set  and  dry ;  the  drying  can  be  facilitated  by  heating 
in  an  oven  or  otherwise. 

The  fusible  metal  of  which  moulds  are  frequently  made  is  an 
alloy  of  five  parts  of  lead,  three  of  tin,  and  eight  of  bismuth,  and 
melts  below  212°  F. 

Care  and  practice  are  requisite  for  producing  a  good  and  sharp 
casting ;  and  the  metal  must  not  be  poured  too  hot.  Commence 
by  pouring  sufficient  of  the  melted  alloy  into  a  suitable  vessel, — 
taking  the  precaution  to  skim  the  dross  from  the  surface  of  it 
with  a  card, — and  when  it  is  nearly  congealed,  bring  the  matrix 
down  upon  it  quickly  and  with  considerable  force,  and  let  it 
remain  until  the  mass  has  perfectly  cooled.  When  done  with 
skill,  a  reverse  will  be  obtained  with  all  the  sharpness  and  per- 
fection of  the  original. 

.  Gutta  percha  is  probably  the  substance  best  adapted  for  taking 
moulds  for  electrotyping.  It  is  applicable  to  metal,  wood,  glass, 
stone,  &c.  It  needs  only  to  be  softened  by  heat  either  in  warm 
water  or  by  a  steam-bath,  spread  into  suitable  form,  laid  and 
pressed  upon  the  object  to  be  copied,  and  allowed  to  cool  under 
the  pressure,  when  the  mould  will  be  fit  for  use. 

Sulphur  is  sometimes  used  for  moulds ;  and  very  beautiful  im- 
pressions can  be  made  also  with  sealing-wax,  which  takes  the 
minutest  lines  of  the  original.  Reverses  may  be  procured  in  lead 
by  forcing  the  matrix  into  a  bright  surface  of  it,  either  by  pres- 
sure or  blows. 

Non-conducting  Substances. — As  gutta  percha,  wax,  plaster 
of  Paris,  and  many  of  the  materials  used  for  making  moulds  are 
non-conductors,  it  is  necessary  to  coat  the  surface  on  which  it  is 
desired  to  deposit  metal  with  some  conducting  substance.  The 
best  and  easiest  of  application  is  plumbago  or  black  lead.  A 
copper  band  or  wire  is  fastened  around  the  edge  of  the  mould, 
and  the  ends  formed  into  a  hook,  or  punched  with  holes,  to  make 
the  connection  with  the  battery.  A  fine  brush  is  dipped  into  the 
plumbago  and  passed  thoroughly  over  the  face  of  the  mould,  all 
excess  of  black  lead  being  carefully  removed,  and  the  brushing 
continued  until  every  part  is  covered  and  brightly  polished.  This 


SOLUTIONS.  569 

treatment  will  insure  a  quick  and  even  deposit.  In  wax  moulds 
it  is  only  necessary  to  insert,  in  the  edge  of  the  mould,  a  piece 
of  copper  by  which  to  attach  it  to  the  battery-pole.  In  every 
case,  however,  the  conducting  coating  must  extend  to  and  be  in 
contact  with  the  battery  connection.  In  using  metal  moulds, 
those  parts  on  which  metal  is  not  to  be  deposited  should  be  covered 
with  wax  or  some  kind  of  varnish. 

The  battery  connection  is  most  conveniently  and  perfectly 
formed  by  soldering  a  copper  wire,  flattened,  at  one  end  to  the 
metal  mould. 

Bronze  powder  is  sometimes  used  instead  of  plumbago  and  in 
the  same  manner.  Flowers,  and  other  objects  to  which  plumbago 
is  not  applicable,  may  be  rendered  conducting  by  a  film  of  gold 
or  silver.  This  is  applied  through  the  medium  of  a  solution  of 
phosphorus  in  bi-sulphuret  of  carbon.  The  solution  is  made  by 
dissolving  1  ounce  of  phosphorus  in  15  ounces  of  bi-sulphuret  of 
carbon,  and  adding  thereto  1  ounce  of  wax,  1  ounce  of  asphalte, 
1  ounce  of  spirits  of  turpentine,  and  1  drachm  of  india-rubber. 
The  india-rubber  must  be  dissolved  in  turpentine,  and  the  as- 
phalte in  the  phosphorus  solution.  The  wax  is  melted  first,  the 
turpentine  and  india-rubber  stirred  in,  and  then  the  asphalte  and 
phosphorus  solution  added. 

This  should  be  done  with  caution  over  a  water-bath,  as  the 
components  are  highly  inflammable.  The  bi-sulphuret  of  carbon 
being  very  volatile,  the  solution  should  be  kept  in  a  well-stoppered 
bottle.  "  The  solution,  as  above  prepared,  is  applied  to  the  sur- 
faces of  non-metallic  substances  by  immersion  or  brushing ;  the 
article  is  then  dipped  in  a  dilute  solution  of  nitrate  of  silver  or  chlo- 
ride of  gold ;  in  a  few  minutes  the  surface  is  covered  with  a  fine  film 
of  metal,  sufficient  to  insure  a  deposit  of  any  required  thickness 
on  the  article's  being  connected  with  a  battery.  The  solution  in- 
tended to  be  used  is  prepared  by  dissolving  1  ounce  of  silver  in 
nitric  acid,  and  afterwards  diluting  with  3  gallons  of  water ;  the 
gold  solution  is  made  by  dissolving  2  pennyweights  of  gold  in 
aqua  regia,  and  then  diluting  with  a  gallon  of  water." 

G-old  Solution. — Convert  a  half  ounce  of  gold  into  terchloride, 
dissolve  the  gold  salt  in  a  little  water,  and  add  it  to  a  solution  of 
four  ounces  of  cyanide  of  potassium  in  two  quarts  of  water  and 
filter. 


570  SOLUTIONS. 

Silver  Solution. — Take  of  cyanide  of  silver  1  ounce,  cyanide 
of  potassium  10  ounces,  water  6  pints ;  dissolve  the  cyanide  of 
potassium  in  the  water,  add  the  cyanide  of  silver,  and  filter  the 
solution. 

Probably  a  better  way  to  make  the  solutions  of  gold  and  silver 
in  cyanide  of  potassium  is  with  the  battery.  Immerse,  in  a  solu- 
tion of  1  part  cyanide  of  potassium  to  16  parts  of  water,  a  silver 
plate,  connected  with  the  positive  pole  of  a  battery,  complete  the 
connection  with  the  negative  pole,  and  keep  up  the  action  of  the 
battery  until  silver  is  freely  deposited  on  the  negative  pole.  The 
same  process  is  followed  for  gold,  care  being  taken  to  substitute 
a  gold  for  the  silver  plate. 

Sulphate  of  Copper  is  the  best  salt  for  the  reduction  of  copper. 
A  nearly  saturated  solution,  acidulated  with  a  few  drops  of  sul- 
phuric acid,  is  used.  One  pound  of  the  sulphate  in  six  pounds  of 
water  is  a  good  strength. 

Cyanide  of  Copper  is  sometimes  used  for  depositing  copper  or 
iron.  It  is  made  by  dissolving  the  oxide  in  an  excess  of  cyanide 
potassium,  or  by  making  a  sheet  of  copper  the  positive  pole  in  a 
solution  of  cyanide  of  potassium. 

Platinum,  zinc,  and  most  of  the  metals  can  be  reduced  from 
their  salts  by  the  battery ;  but  for  electrotyping  they  are  seldom 
or  never  used. 

To  have  the  metals  adhere  well  in  gilding  and  silvering,  the 
articles  to  be  plated  must  be  well  cleansed.  As  silver  is  gene- 
rally precipitated  on  copper,  the  article  is  boiled  in  caustic  potash 
or  soda  well  rinsed  with  water,  dipped  in  dilute  nitric  acid,  after- 
wards immersed  in  a  weak  solution  of  nitrate  of  mercury,  and 
immediately  placed  in  the  silvering  solution.  Gold  is  usually 
deposited  on  silver.  The  silver  object  is  treated  as  before  with 
caustic  lye,  rinsed,  and,  when  dry,  is  thoroughly  scratched  with 
a  scratch-brush,  which  is  a  bunch  of  fine  wires  made  into  a  brush. 
It  is  then  ready  for  the  battery.  In  gilding,  the  solution  should 
be  maintained  at  about  150°  F.  by  a  water-bath. 

To  avoid  opposite  currents  of  electricity  in  the  depositing  solu- 
tion from  an  exhaustion  of  the  solution  around  the  negative  pole, 
and  a  dense  solution  forming  around  the  positive  pole,  the  articles 
should  be  kept  in  motion  during  the  deposition;  for  this  motion 
also  prevents  that  crystalline  deposit  deemed  so  objectionable. 


BRONZING. 


571 


To  prevent  the  adhesion  of  the  matrix  to  the  deposited  metal, 
Mr.  Mathiot,  of  the  United  States  Coast  Survey,  recommends 
that  the  engraved  copper  plates,  &c.,  be  coated  in  a  battery  with 
a  thin  film  of  silver,  and  afterwards  washed  with  a  dilute  solution 
of  iodine  in  alcohol, — about  one  grain  of  the  former  in  a  quart  of 
the  latter. 

Dusting  with  black  lead,  or  spreading  a  little  oil  over  the  sur- 
face of  the  article,  care  being  taken  not  to  use  an  excess,  will 
cause  the  metals  to  separate  easily.  A  little  wax  dissolved  in 
spirits  of  turpentine  also  answers  well. 

Solutions  should  be  kept  covered  from  the  air  and  dust;  and 
the  working  of  the  batteries  is  promoted  by  having  the  surrounding 
atmosphere  of  a  warm  temperature. 

A  few  drops  of  bi-sulphuret  of  carbon  added  to  a  silver  solu- 
tion will  produce  a  bright  deposit. 

In  inserting  the  articles  in  the  solutions  the  air  adhering  to 
their  surfaces,  and  which  prevents  a  contact  of  the  metals,  may  be 
dispelled  by  moving  the  articles  about  in  the  liquid  or  by  heating 
the  solution. 

Fig.  475. 


The  plates  attached  to  the  positive  poles  should  be  parallel  to 
the  articles  on  which  the  metal  is  to  be  deposited  and  present  the 
same  amount  of  surface. 

A  battery,  if  in  proper  working  order,  will,  when  the  connec- 


572  BLOWPIPE   MANIPULATIONS. 

tions  are  made,  show  a  disengagement  of  gas  at  its  negative 
metal ;  but  no  gas  should  be  seen  to  escape  at  either  pole. 

Bronzing. — To  give  the  copies  of  medals  and  other  objects  an 
antique  or  bronzed  appearance  like  the  original,  several  means 
are  employed.  A  dark  bronze  is  produced  by  dipping  the  object 
in  very  dilute  nitric  acid, — say  half  an  ounce  of  acid  to  a  pint 
of  water, — and,  after  drying,  heating  it  gradually  and  uniformly. 
The  color  is  deepened  in  proportion  to  the  heat  applied.  Sul- 
phuretted hydrogen  or  hydrosulphuret  of  ammonia  may  also  be 
used.  Afterwards  polish  with  a  brush.  Green  bronzes  are 
formed  by  immersing  the  articles  in  a  solution  of  chloride  of 
ammonium  or  chloride  of  sodium,  or  by  exposing  them  to  the 
fumes  of  chloride  of  lime.  The  depth  of  the  bronze  is  regulated 
by  the  length  of  time  during  which  the  articles  are  subjected  to 
the  galvanic  action.  A  coating  of  black  lead  and  subsequent 
heating  of  the  article,  gives  a  beautiful  bronze.  A  thin  film  of 
oil  or  wax,  and  heating  until  the  grease  commences  to  decompose, 
produces  a  good  bronze.  Immersion  in  a  solution  of  chloride  of 
platinum  also  gives  a  handsome  bronze. 


CHAPTER  XXIX. 

BLOWPIPE   MANIPULATIONS. 

THE  blowpipe  is  a  small  and  convenient  instrument  by  which  a 
blast  of  air  may  be  forced  through  a  candle,  or  oil  or  gas  flame,  so 
as  to  intensify  the  heat  of  the  latter  to  such  an  extent  as  to  render 
it  a  substitute  for  the  furnace  in  very  minute  and  delicate  ope- 
rations. 

Its  use  had  long  been  known  in  the  arts,  but  its  first  applica- 
tion to  chemistry  was  made,  in  1738,  by  Anthony  von  Schwab,  a 
Swedish  Counsellor  of  the  College  of  Mines.  He  employed  it  in 
testing  ores  and  minerals,  but  not  having  left  any  account  of  his 
experiments,  we  are  ignorant  how  far  they  extended. 

In  the  hands  of  Cronstedt,  a  Swedish  Master  of  Mines,  it  be- 
came a  ready  means  of  distinguishing  and  arranging  minerals 
according  to  their  characteristic  behavior  with  fusible  reagents. 

Von  Engestrom  published,  in  1770,  an  English  translation  of 


BLOWPIPE   MANIPULATIONS.  573 

Cronstedt's  system  of  mineralogy,  with  an  account  of  the  methods 
employed  by  him  in  testing  minerals;  hut  yet  the  instrument 
found  no  general  favor,  and  for  a  long  time  afterwards  had  no 
more  extended  application  than  to  the  testing  of  the  fusibility  of 
substances,  and  their  solubility  in  borax-glass. 

Bergmann  enlarged  the  sphere  of  usefulness  of  the  blowpipe, 
and  employed  it  in  analytical  investigations,  to  detect  the  pre- 
sence of  minute  quantities  of  certain  mineral  substances.  His 
work  on  the  use  of  the  blowpipe  appeared  in  1779.  Bergmann's 
feeble  health  caused  him  to  seek  the  assistance  of  Gahn  in  his 
experiments,  who  became,  under  his  instruction,  so  expert  in  the 
use  of  the  blowpipe  that  he  was  able  to  detect  with  it  substances 
which  had  escaped  the  most  careful  analysis  in  the  moist  way. 
But  Gahn  could  never  be  prevailed  to  give  to  the  world  the  re- 
sults of  his  experience.  Fortunately  for  science,  his  pupil,  Ber- 
zelius,  recognized  the  value  of  this  instrument,  and  after  testing 
with  it  the  reactions  of  most  of  the  minerals  and  mineral  sub- 
stances then  known,  published  his  valuable  work  on  "The  use  of 
the  Blowpipe  in  Chemistry  and  Mineralogy." 

After  the  publication  of  this  work,  in  1821,  the  use  of  the  blow- 
pipe become  general  among  chemists  and  mineralogists.  Harkort 
first  attempted  to  make  quantitative  assays  with  its  assistance; 
but  it  is  to  Plattner,  Professor  of  Metallurgy  in  the  Saxon  Royal 
School  of  Mines,  that  the  method  of  performing  quantitative  de- 
terminations by  the  blowpipe  owes  its  great  exactness  and  sim- 
plicity. His  admirable  work  "  On  the  Art  of  Assaying  with  the 
Blowpipe,"  furnishes  the  most  accurate  and  complete  information 
on  this  branch  of  science,  and  will  be  a  lasting  monument  to  his 
patient  industry  and  genius. 

A  simple  form  of  the  blowpipe,  and  that  originally  adopted  for 
soldering,  &c.,  by  metal-workers,  is  repre- 

fjo^  476. 

sented  in  Fig.  476.     It  consists  of  a  taper-      ^  n 

ing  tube  of  brass,  curved  nearly  at  a  right   (F 
angle,  a  short  distance  from  the  smaller 
end.     The  bore  terminates  in  a  very  small  perforation.    A  steady 
stream  of  air  is  forced  through  it  by  the  action  of  the  muscles  of 
the  cheeks,  and  directed  against  the  flame  of  a  candle  or  lamp. 
This  form  of  the  blowpipe  has  the  disadvantage  of  promoting,  by 
long-continued  blowing,  the  condensation  of  the  moisture  of  the 


574 


BLOWPIPE   MANIPULATIONS. 


breath  in  the  tube.  This  obstructs  the  passage  of  air,  or,  being 
driven  out  into  the  flame,  very  seriously  interferes  with  the  suc- 
cess of  the  operation.  It,  therefore,  becomes  necessary  to  con- 
struct the  blowpipe  with  a  chamber  in  which  the  condensed 
moisture  may  lodge. 

The  instrument  which  best  fulfils  all  the  requirements  for 
general  use  is  that  devised  by  Gahn,  and  recommended  by  Ber- 
zelius. 

It  consists  of  a  slightly  tapering  tube  (Fig.  477),  fitting  into  a 

Fig.  477. 


cylindrical  chamber,  an  inch  long,  and  half  an  inch  in  diameter. 
Into  the  side  of  this  chamber,  a  much  shorter  and  smaller  tube  is 
inserted  at  a  right  angle.     The  end  of  this  tube  is  covered  with  a 
tip  of  platinum,  Fig.  478,  with  a  fine  aperture.     Plattner 
^        recommends  two  such  tips,  with  perforations  of  different 
Oj       dimensions.    The  finest,  which  is  used  in  qualitative  tests, 
has  an  aperture  O4  millimetre  in  diameter.     The  other, 
for  such  tests  as  require  a  stronger  heat,  has  a  slightly  larger 
aperture.     Tips  of  platinum  are  preferable  to  those  made  of  any 
other  metal,  on  account  of  the  facility  with  which  they  may  be 
freed  from  soot  by  heating  them  on  charcoal.     If  tips  of  brass  or 
silver  are  employed,  the  aperture  may  be  cleaned  with  a  fine 
splinter  of  horn.     The  length  of  the  blow- 
pipe must  be  adjusted  to  the  sight  of  the 
operator,  so  that  the  test  object  may  be 
held  at  such  a  distance  as  to  be  distinctly 
visible.     The  blowpipe  should  be  provided 
with  a  mouth-piece  of  ivory  or  horn  a  b, 
Fig.  479.     The  form  of  the  mouth-piece 
recommended    by    Plattner    is    trumpet- 
shaped,  and  it  is  to  be  pressed  against  the 
lips  instead  of  being  held  between  them. 
The  outer  edge  must  have  a  sufficient  spread  to  present  a  flat 


Fig.  479. 


BLOWPIPE   MANIPULATIONS. 


575 


Fig.  480. 


surface  to  the  lips,  so  that  any  undue  pressure  may  be  avoided. 
The  diameter  of  this  mouth-piece  should  not  exceed  one  and  one- 
fourth  to  one  and  one-half  inches. 

The  use  of  this  mouth-piece  very  much  diminishes  the  fatigue 
of  the  muscles  of  the  lip  in  long-continued  blowing,  and  the  diffi- 
culty at  first  felt  in  preventing  the  escape  of  air  at  the  corners  of 
the  mouth  is  easily  overcome  by  practice.  The  drawing  exhibits 
it  in  full  size. 

Mitscherlich  has  so  modified  the  form  of  Gahn's  blowpipe  as  to 
render  it  very  portable.  The  moisture- 
chamber  is  diminished  in  length,  and  per- 
manently attached  to  the  long  tube,  as 
shown  in  the  drawing,  Fig.  480.  This 
tube  is  made  to  unscrew  in  the  middle, 
so  that  the  small  tube  c,  with  its  plati- 
num jet  D,  can  be  slid  into  the  part  con- 
nected with  the  chamber,  and  the  other 
half  A  passed  over  it  as  a  cover.  The 
whole  forms  a  short,  smooth  cylinder,  which 
may  conveniently  be  carried  in  the  pocket. 
The  mouth-piece  should  be  silvered ;  or  a 
separate  mouth-piece  of  ivory  may  be  made 
to  screw  into  it. 

For  the  purpose  of  relieving  the  cheek  muscles  at  intervals, 
without  interruption  to  the  blast,  the  blowpipe  may  be  constructed 
according  to  De  Luca's  suggestions,  and  as  exhibited  in  the  an- 
nexed drawing,  Fig.  481.  Between  the  mouth-piece  and  the 

Fig.  481. 


chamber  for  collecting  the  moisture,  an  india-rubber  bulb  or  bag 
is  adjusted  by  ivory  collars  upon  the  tubes  D  and  H,  the  project- 
ing ends  of  which  are  connected  by  means  of,  a  light  metal  rod. 
The  escape  of  air,  when  the  mouth  may  be  removed,  is  prevented 
by  a  valve  at  A  opening  outwards. 


576  THE   COMBUSTIBLE. 

The  proper  material  for  the  construction  of  blowpipes  is  real 
or  German  silver.     When  made  of  the  latter,  it  will  be  advisable 
to  galvano-plate  them,  otherwise  the  base  metal,  by  constant 
handling,  will  impart  an  unpleasant  odor,  and  dirty  the  skin. 
The  great  conducting  power  of  both  of  these  materials  is  apt  to 
cause  the  instrument  to  become  overheated  by  a  long-continued 
blowing.     Brass  blowpipes  are  very  objectionable,  as  they  oxidize 
readily  at  the  jet,  and  moreover  give  a  metallic  taste  and  odor. 
In  emergencies,  a  very  convenient  blowpipe  may  be  made  from 
a  common  tobacco-pipe,  by  accurately 
Flg>482-  closing  the  bowl  with  a  tight  cork,  and 

fitting  in  the  latter  a  glass  jet.     This 
latter  is   formed   by  drawing  out  a 
small  tube  to  a  fine  point,  and  smooth- 
ing the  end  in  the  flame  until  it  be- 
comes thick,  but,  at  the  same  time,  presents  a  perfectly  round 
and  small  aperture. 

The  Combustible. — Almost  any  flame  which  is  strong  enough 
to  afford  the  requisite  heat  may  be  used  with  the  blowpipe.  In  labo- 
ratories where  coal-gas  is  burned,  its  use  will  be  found  very  con- 
venient. The  form  of  burner  which  we  have  found  to  answer 
best  is  that  known  as  Solliday's  patent,  a  single  slit  burner,  with 
a  small  cylinder  fitting  closely  around  it,  and  reaching  a  short 
distance  above  the  base  of  the  flame.  This  cylinder,  or  jacket, 
has  two  shallow  incisions  lying  in  the  axis  of  the  flame,  in  one  of 
which  the  jet  of  the  blowpipe  may  be  made  to  rest.  For  very 
small  operations  the  flame  of  a  candle  may  be  employed ;  but  for 
many  reactions  it  does  not  yield  sufficient  heat,  and  in  quantita- 
tive assays  its  use  is  quite  inadmissible.  The  best  fuel  for  this 
purpose  is  olive,  or  refined  rape  oil.  Care  must  be  taken  to  select 
oil  which  burns  without  much  smoke,  and  with  a  colorless  flame, 
as  the  color  of  the  flame  is  frequently  a  characteristic  reaction. 

Harkort's  modification  of  Berzelius's  lamp  is  the  most  conve- 
nient and  best  adapted  for  blowpipe  experiments.  It  consists  of  a 
sheet  brass,  horizontal  cylinder,  four  and  a  half  inches  long,  and 
slightly  tapering  to  one  inch  width  at  the  end  nearest  the  ope- 
rator, as  shown  in  Fig.  483. 

It  is  made  to  slide  upon  an  upright  brass  rod,  and  can  be  ad- 
justed to  any  height  by  a  screw.  At  one  end  of  the  lamp  is  an 


HARKORT'S  LAMP. 


577 


opening  for  introducing  oil,  and  at  the  other  is  the  wick-holder. 
Both  of  these  openings  are  closed  by  screw-caps,  with  the  thread 

Fig.  483. 


cut  on  the  inside.  The  escape  of  oil  is  prevented  by  washers 
cemented  to  the  caps  with  shell-lac  and  wax.  The  wick-holder 
has  its  greatest  breadth  at  right  angles  to  the  axis  of  the  lamp, 
and  must  be  cut  off  obliquely,  to  allow  the  flame  to  be  directed 
downwards.  Cylindrical  woven  wicks,  such  as  are  made  for  Ar- 
gand  burners,  are  best  adapted  for  this  lamp,  and  they  are  pressed 
flat  and  folded  lengthwise,  so  as  to  be  introduced  fourfold.  Care 
must  be  taken  that  the  wick  does  not  fit  too  tightly,  else  its  capil- 
larity will  be  impaired,  and  the  ascent  of  the  oil  obstructed. 


Moreover,  the  wicks  must  be  entirely  free  from  any  lime  that, 
may  have  been  used  in  the  bleaching  of  them,  as  that  earth, 

3T 


578  THE   FLAME. 

"    rf» 

in  giving  a  reddish-yellow  flame  itself,  may  obscure  the  flame  re- 
action of  the  substance  under  process. 

The  r6d  in  which  the  lamp  slides  also  carries  a  triangle,  which 
is  very  convenient  for  supporting  small  capsules,  crucibles,  &c., 
over  the  flame.  To  render  the  apparatus  compact  and  portable, 
it  is  constructed  in  parts,  with  screw  connections.  Fig.  485  shows 
the  several  pieces  in  their  proper  positions. 

In  addition  to  the  above,  a  small  spirit-lamp  is  often  needed 
for  applying  a  flame  directly  to  tubes,  crucibles,  &c.,  Fig.  484. 

The  blowpipe  is  held  in  the  right  hand,  as  shown  in  Plate  3, 
and  in  such  a  manner  as  to  facilitate  a  direction  of  the  flame 
upon  the  substance  under  process.  This  latter,  as 

Fig.  485.      wjjj  ke  geen  jn  t^e  same  (Jrawing)  is  nel(j  upon  a 

support  by  the  left  hand  ;  care  being  taken  to  retain 
the  arms  in  their  fixed  position,  for  unsteadiness 
will  prevent  an  uninterrupted  action  of  the  blast  in 
the  assay. 

The  mouth  furnishes  the  blast,  which  derives  its 
force  from  the  muscles  of  the  cheek.  To  prevent 
fatigue  of  the  respiratory  organs,  communication 
between  the  mouth  and  chest  must  be  closed  during 
the  blowing,  and  breathing  maintained  through  the 
nostrils.  A  few  days'  practice  removes  all  the  difficulty  at  first 
experienced  in  producing  a  continuous,  steady  current ;  and  it  is 
by  this  means  only  that  proficiency  can  be  acquired.  The  ope- 
ration is  commenced  by  filling  the  mouth  with  air,  expanding  the 
cheeks,  and  then  keeping  up  a  steady  forcible  pressure  with  the 
muscles,  respiration  being  allowed  to  go  on  as  usual  through  the 
nose. 

The  Flame. — The  flame  which  furnishes  the  heat  for  blowpipe 
operations  consists  of  several  parts,  of  each  of  which  it  is  neces- 
sary to  have  a  knowledge  in  order  to  be  able  to  manage  it  skil- 
fully. Flame  may  be  considered  as  a  miniature  furnace,  pro- 
ducing an  intense  heat  with  the  aid  of  a  blowpipe.  It  consists  of 
four  distinct  parts,  as  will  be  explained  by  the  drawing,  Fig.  486, 
which  represents  an  oil  or  tallow  flame.  The  base  a  b  is  a  dis- 
tinct blue  conical  envelope  surrounding  the  burning  wick,  and 
which  gradually  diminishes  as  it  rises,  and  eventually  disappears 
when  it  reaches  the  point  where  the  flame  elongates  perpendicu- 


I 


*.T 


°"w,. , 


„•;  *-.:•  if   W 


?*-     . .  •:/< 


THE   FLAME. 


579 


Fig.  486. 


larly.  The  central  portion  is  the  dark  cone  <?,  sur- 
rounded by  the  brilliant,  luminous  envelope  d,  which 
is  the  sphere  of  illumination.  Exterior  to  this,  and 
enveloping  the  whole  is  the  faintly  luminous  cur- 
tain a  e  I,  forming  the  hottest  portion  of  the  flame, 
and  presenting  its  greatest  intensity  at  the  point/. 
From  this  point  the  heat  gradually  diminishes,  both 
upwards  and  downwards. 

The  structure  of  the  flame  is  explicable  as  follows. 
The  wick  being  an  assemblage  of  threads,  exercises, 
when  lighted,  the  power  of  capillarity,  arid  continu- 
ously draws  up  the  fluid  fat  to  the  accendible  point, 
where  the  elements  of  the  latter,  carbon,  oxygen,  and  hydrogen, 
are  resolved  by  combustion  into  inflammable  gases,  which  burn  and 
produce  flame.  The  external  part  a  e  b  is  the  hottest,  owing  to  its 
direct  contact  with  the  air,  which  supplies  oxygen  to  complete  the 
burning  of  those  products  which  rise  from  the  wick  through  the 
flame  as  faintly  luminous  matter,  and  in  a  state  of  partial  combus- 
tion. As  before  said,  this  portion  gives  its  maximum  of  heat  at  the 
level  of//.  The  coolest  part  of  the  flame,  on  the  other  hand,  is  at 
a  6,  and  its  blue  color  is  due  to  the  combustion  of  carbonic  oxide 
and  a  small  portion  of  carburetted  hydrogen.  The  shaded  cone 
in  the  centre  is  the  sphere  of  unburned  combustible,  owing  to  the 
difficult  access  of  the  air  to  it ;  and  surrounding  it  is  the  brilliant 

Fig.  487. 


portion,  less  favored  with  oxygen  from  the  air  than  the  exterior 
sphere  of  complete  combustion  on  which  it  impinges. 


580  OXIDATION. 

When  a  current  of  air  is  directed  through  a  blowpipe  with  a 
small,  straight  aperture  against  a  flame,  it  drives  the  latter  be- 
fore it  in  a  long,  pointed,  and  conical  projection.  To  produce  a 
clean  and  uniform  flame,  the  tip  end  of  the  blowpipe  should 
barely  penetrate  the  flame,  Fig.  487,  and  when  it  is  desired  to 
give  it  volume,  it  must  be  slightly  parted  in  the  middle  by  draw- 
ing the  tip  of  the  blowpipe  across  it.  In  this  latter  case,  too,  the 
blowpipe  should  be  directed  at  an  angle  of  forty-five  degrees 
across  this  channel.  In  blowing,  the  breath  must  be  so  regu- 
lated that  the  blast  should  be  neither  too  strong  nor  too  feeble ; 
for,  in  the  first  instance,  the  excessive  air  cools  the  flame,  and  in 
the  latter,  the  combustion  is  slow  and  imperfect. 

"  The  long,  narrow  blue  flame  a  6,  which  appears  directly  be- 
fore the  jet,  is  the  same  as  a  5,  Fig.  486,  although  changed  in 
form,  being  now  concentrated  into  a  small  cylindrical  space, 
whereas  before  it  formed  an  envelope  around  the  whole  flame. 
Just  before  the  point  of  this  blue  flame  is  the  greatest  heat,  just 
as  in  a  free  flame,  but  with  this  difference,  that,  in  the  latter  case, 
it  formed  a  ring  around  the  flame,  while,  in  the  former,  it  is  con- 
centrated into  a  focus.  It  is  thus  rendered  sufficiently  intense 
to  fuse  and  volatilize  substances  which  were  not  sensibly  acted  on 
by  the  flame  in  its  usual  state.  On  this  is  founded  the  whole 
theory  of  the  intense  heat  produced  by  the  blowpipe ;  the  effect 
which  would  otherwise  be  distributed  over  the  whole  surface  of 
the  flame  is  concentrated  into  a  small  space,  exactly  as  if  the 
flame  had  been  turned  inside  out.  The  surrounding  illuminating 
portion  of  the  flame  prevents  the  heat  from  escaping. 

"  Long  practice  is  required  to  know  where  the  maximum  of 
heat  is,  since  different  substances  are  differently  ignited,  and  the 
light  which  they  emit  is  often  deceptive.  A  very  intense  heat 
is  required  when  the  fusibility  of  a  substance  is  to  be  investigated, 
or  when  different  metallic  oxides,  which  are  obstinate  in  parting 
with  their  oxygen,  like  the  oxides  of  tin  or  iron,  are  to  be  reduced. 
But  it  is  not  a  high  temperature  only  which  it  is  the  design  of 
the  blowpipe  to  produce ;  there  are  other  operations  which  require 
a  less  intense  heat,  and  which,  though  diametrically  opposed  to 
each  other,  can  be  effected  by  the  blowpipe.  These  are  oxidation 
and  reduction." 

Oxidation. — "This  takes  place  when  the  assay  is  heated,  just 


REDUCTION.  581 

before  the  extreme  point  of  the  flame,  when  all  the  combustible 
particles  are  completely  oxidized.  The  farther  from  the  apex 
of  the  blue  flame,  the  better  the  operation  goes  on,  provided  the 
heat  be  sufficiently  intense ;  and  it  must  be  observed  that  a  too 
high  temperature  often  impedes  the  oxidation,  especially  if  the 
assay  be  supported  upon  charcoal.  Oxidation  goes  on  best  at  a 
low  red  heat ;  and  to  this  end  the  blowpipe  jet  must  have  a  large 
aperture." 

Reduction. — "  This  process  succeeds  best  with  a  fine  jet,  which 
should  not  be  inserted  too  far  in  the  flame,  since,  in  this  case,  a 
highly  illuminating  flame  is  produced,  the  elements  of  which,  not 
undergoing  complete  combustion,  do  not  take  oxygen  from  the 
assay,  which  may  be  considered  as  being  heated  in  an  inflam- 
mable gas.  If,  in  the  course  of  the  operation,  the  assay  becomes 
coated  with  soot,  it  is  a  proof  that  the  flame  is  too  smoky,  and, 
consequently,  its  heat  is  diminished.  The  blue  flame  was  formerly 
regarded  as  the  proper  reducing  flame ;  this  is,  however,  untrue, 
for  it  is  the  brilliant  portion  of  the  flame  which  causes  deoxida- 
tion ;  but  the  assay  must  be  held  in  it  in  such  a  manner  as  to  be 
surrounded  by  it  on  all  sides  and  protected  from  contact  with  the 
air.  It  is  to  be  remembered,  that  reduction  is  accomplished,  not 
by  the  charcoal,  but  by  the  combustible  atmosphere  which  sur- 
rounds the  assay.  The  reduction  which  takes  place  at  the  points 
of  contact  of  the  assay  and  the  charcoal  would  happen  equally 
as  well  in  the  outer  as  in  the  inner  flame. 

"  The  most  important  matter  is  to  be  able  to  produce,  option- 
ally, oxidation  or  reduction ;  and  this  is  soon  acquired  by  prac- 
tice. Oxidation  is  so  easily  performed  that  it  is  only  necessary 
to  be  told  how  to  do  it.  Reduction  requires  more  experience,  and 
a  better  knowledge  of  the  management  of  the  flame.  It  is  an 
excellent  exercise  to  fuse  a  small  grain  of  tin  upon  charcoal,  and 
raise  it  to  a  white  heat,  while  keeping  its  surface  brilliant.  Tin 
has  an  attraction  for  oxygen  so  strong,  that  the  moment  the  flame 
is  changed  in  the  least  the  metal  becomes  covered  with  an  in- 
fusible crust  of  oxide  of  tin.  The  larger  the  globule  of  tin  that 
the  operator  is  able  to  keep  fused  in  the  metallic  state,  the  more 
proficient  is  he  in  the  management  of  the  blowpipe  and  the 
flame." 

The  wick  of  the  lamp  must  be  cut  evenly  and  free  from  fibres, 


582  SUPPORTS. 

and  the  blast  must  be  uninterrupted,  more  particularly  in  the 
reducing  process. 

Supports. — The  substance  under  examination  must  be  allowed 
to  rest  firmly  upon  a  support,  which  should  be  such  as  will  not 
fuse  under  a  high  heat,  combine  chemically  with  the  fused  body, 
or  prevent  its  complete  heating  by  rapid  conduction.  The  sup- 
ports in  most  common  use  are  charcoal,  and  platinum  either  in 
the  form  of  wire  or  foil. 

Charcoal  makes,  for  many  operations,  an  excellent  support, 
especially  that  kind  of  it  which  is  made  from  well-grown  pine 
wood,  or  the  branches  of  the  willow.  It  must  be  well  charred, 
and  that  which  snaps  or  smokes  in  the  fire  should  be  rejected.  It 
is  desirable  that  it  shall  be  as  free  as  possible  from  ashes,  which 
nearly  always  contain  a  trace  of  iron  and  manganese ;  therefore 
dense  and  compact  woods  should  not  be  used,  as  they  give  much 
ashes,  and  often  contain  a  considerable  amount  of  these  oxides, 
which,  by  uniting  with  the  fluxes  employed,  would  give  incorrect 
results.  Straight  pieces,  free  from  knots,  are  to  be  sawed  in  the 
direction  of  the  fibres,  into  oblong  supports  of  the  proper  size. 
The  saw  for  cutting  the  charcoal  should  have  fine  teeth  and  a 
blade  of  five  inches  length,  three-eighths  of  an  inch  breadth,  and 
one-sixteenth  of  an  inch  thickness.  The  assay  is  placed  in  a 
shallow  concavity,  made  near  one  end  of  such  a  support  by  the 
borer  or  point  of  a  knife ;  and  upon  this  substance,  so  prepared, 
oxidation,  reduction,  and  fusion  are  chiefly  performed. 

Sometimes  the  reducing  property  of  charcoal,  and  the  rapidity 
with  which  it  is  dissipated  into  carbonic  acid,  interfere  with  the 
result.  In  such  cases,  platinum  in  the  form  of  foil  or  wire  is  used. 
A  narrow  strip,  3  inches  long  and  J  inch  broad,  is  often  advan- 
tageously employed  for  oxidation.  The  substance  which  is  to  be 
oxidized,  is  placed  on  it  near  one  end,  and  heat  is  applied  by  the 
blowpipe  flame  upon  its  under  side.  Its  conducting  power  is  so 
inconsiderable,  that  the  other  end  may  be  held  between  the  fin- 
gers without  inconvenience.  Platinum  cannot  in  general  be  used 
for  reduction,  as  it  forms  fusible  alloys  with  some  of  the  metals ; 
nor  should  sulphurets,  arseniurets,  &c.,  be  heated  in  contact  with 
it.  When  the  strip  is  too  short  to  be  held  between  the  fingers,  it 
can  be  inserted  in  a  piece  of  wood  or  charcoal,  or  be  held  between 
the  points  of  a  pincette.  A  small  spoon  of  the  same  metal  is 


SUPPORTS.  583 

sometimes  made  use  of;  but  in  the  majority  of  cases,  the  wire 
may  be  substituted  for  any  other  means. 

When  platinum  wire  is  used,  it  should  be  about  2  J  inches  long, 
moderately  thin,  and  bent  into  a  hook  at  one  end,  which 
serves  as  the  support  for  the  assay.     This  part  is  either    Fig.  488. 
heated  for  a  moment  in  the  flame,  or  moistened  and  dip- 
ped into  the  flux,  whereby  a  small  quantity  becomes 
attached,  which,  when  fused  to  a  transparent  bead  by  the 
blowpipe  flame,  becomes  firmly  fixed  in  its  bed,  and  oc- 
cupies the  space  within  the  curve.     The  side  of  the  bead 
is  then  moistened,  and  a  little  of  the  assay  is  made  to 
adhere  to  it. 

Both  are  now  fused  together,  and  the  appearance  of  the  bead 
held  in  one  or  the  other  part  of  the  flame,  in  reference  to  opacity, 
color,  and  other  characteristics,  can  be  distinctly  seen  from  all 
sides,  and  in  this  way  are  colorations  of  the  bead  by  metallic 
oxides  particularly  to  be  distinguished.  The  only  objection  to 
this  hooked  wire,  occurs  in  the  case  of  the  use  of  fusible  flux, 
which  is  apt  to  fall  through  it.  Two  or  three  additional  turns  of 
the  hook  will  generally  make  a  bed  sufficiently  close  to  prevent 
this  salt  from  running  through  when  fused. 

The  bead  can  be  detached  from  the  wire,  when  cold,  by  a  slight 
blow  with  the  hammer.  If,  after  its  removal,  the  wire  is  not  left 
perfectly  clean,  a  bead  of  soda  may  be  fused  upon  it,  and  after- 
wards dissolved  out,  when  it  takes  the  impurities  with  it.  In 
extensive  investigations,  by  means  of  the  blowpipe,  a  number  of 
these  wires  should  be  provided. 

Fig.  489. 


The  wire  may  be  held  in  the  hand,  either  with  or  without  a  hilt ; 
but  it  is  more  convenient  to  use  the  latter.  It  is  nothing  more 
than  a  turned  piece  of  wood,  Fig.  489,  with  a  metallic  socket  on 
the  end  for  receiving  the  wire,  which  is  then  fastened  in  by  the 
screw  B. 


584 


DETECTION  OF  VOLATILE  SUBSTANCES. 


Fig.  490. 


A  support  for  cupels  and  small  crucibles  is  shown  by  Fig. 

490.  It  is  a  piece  of  turned  wood,  3J  inches  long,  with  a  brass 
wire,  fashioned,  as  is  seen,  for  receiving  the 
cupel  and  holding  it  firmly  during  the  action 
of  the  blowpipe.  The  handle  allows  the 
operator  to  change  its  position  before  the 
flame,  merely  by  turning,  raising,  or  lowering 
it,  as  may  be  necessary. 

A  small  platinum  spoon,  from  3-  to  f  inches 
diameter,  and  of  form  shown  by  Fig.  491,  will 
be  required,  as  the  containing  vessel,  in  flux- 
ing ores.  It  is  made  with  a  projecting  strip 
from  the  bowl,  by  which  it  is  adjusted  in  the 
handle,  Fig.  489,  on  preceding  page. 

A  well-polished  ivory  or  platinum  spoon, 
Fig.  492,  about  three  inches  long  and  three-six- 
teenths of  an  inch  in  breadth,  will  be  necessary 
in  weighing  the  powdered  ore,  and  mixing  it 
with  the  flux.  The  handle  should,  for  greater 
convenience,  be  made  in  the  form  of  a  spatula. 
Detection  of  Volatile  Substances  by  means  of  the  Blowpipe. 

— When  volatile  substances  or  gaseous  products  are  to  be  tested 

Fig.  491. 


by  means  of  this  instrument,  the  body  to  be  examined  is  usually 
exposed  to  heat  in  an  open  glass  tube,  which  may  be  from  two  to 


Fig.  .492. 


four  inches  in  length,  and  from  the  twelfth  to  the  third  of  an  inch 
in  diameter.     The  body  is  placed  near  to  one  end,  and  the  blast 


INSTRUMENTS   USED   IN   BLOWPIPE  ANALYSIS. 


585 


is  directed  upon  it,  while  the  tube  (Fig.  493)  is  inclined  more  or 
less  in  proportion  to  the  current  of  air,  which  is  required  to  be 
passed  through  it.  By  such  means,  disengaged  vapors  may  be 
sometimes  recognized  as  they  emerge  from  the  upper  end,  and 
volatile  matters  condensed  upon  a  part  of  the  tube. 

It  is  often  necessary  to  deposit  the  substance  in  the  angle  of  a 
curved  tube,  so  as  to  prevent  it  from  falling  out.  A  tube  so  bent 
is  shown  at  5,  Fig.  494.  Another  modification  is  required  where 


Fig.  493. 


Fig.  494. 


the  access  of  much  or  any  air  would  counteract  the  intention  of 
the  operator,  by  oxidizing  the  body.  In  such  cases,  the  lower 
end  of  the  tube  is  either  completely  closed,  or  drawn  out  to  a 
fine  orifice  as  at  c  in  the  same  figure.  A  tube  of  this  form  is 
well  adapted  to  the  sublimation  of  selenium  from  a  sulphuret, 
where  the  entrance  of  much  air  would  oxidize  it.  Decrepitating 
substances  should  also  be  heated  in  tubes  closed  at  one  end,  and 
should  be  so  inclined  as  to  avoid  loss  of  particles.  For  such  and 
many  other  purposes,  tubes,  Fig.  484,  enlarged  into  a  bulb  at  one 
extremity,  are  very  appropriate. 

All  the  glass  tubes  and  vessels  employed  in  this  way  should  be 
perfectly  free  from  lead. 

The  following  instruments  are  also  used  in  making  examina- 
tions with  the  blowpipe ; — steel  forceps  with  the  points  made  of 
platinum,  for  holding  the  assay  in  the  blowpipe  flame  to  ascertain 
its  fusibility  or  other  properties  when  exposed  to  an  elevated  tem- 
perature. The  two  upper  drawings  of  Fig.  495  represent  different 
views  of  an  excellent  forceps,  capable  of  very  general  applica- 
tion. Two  strips  of  steel,  with  narrow  platinum  points,  &,  £>,  are 
fastened  in  the  middle  by  a  piece  of  metal  seen  at  ej  e.  These 
strips  separated,  as  seen  in  the  figure,  constitute  a  double  pair, 
one  being  at  a,  a,  and  the  other  at  c.  The  platinum  points,  by 


586  INSTRUMENTS   USED   IN   BLOWPIPE   ANALYSIS. 

the  elasticity  of  the  metal  of  which  the  forceps  are  made,  are 
always  closed.  To  open  them  it  is  only  necessary  to  compress 
with  the  thumb  and  finger  the  small  projections  with  the  button 
heads  d,  d,  which  are  connected  with  the  strips  opposite  to  them. 
Upon  relaxing  the  pressure,  the  assay  is  forcibly  held  between  the 
points.  The  points  a  a  are  tempered,  and  are  used  for  detach- 
ing exceedingly  small  fragments  of  the  mineral. 

Fig.  495. 


Another  form  of  this  instrument  is  employed,  but  its  use  is  not 
quite  as  convenient  as  that  of  the  one  just  mentioned.  Its  points 
b  c  are  also  of  platinum,  but  curved  a  little,  as  represented  in  the 
figure.  The  legs  are  made  of  brass.  The  forceps  is  kept  open 
by  the  elasticity  of  the  metal,  and  closed  by  a  double  button  d, 
which  slides  up  and  down  in  a  slit  cut  in  the  legs.  As  brass  is  a 
good  conductor  of  heat,  two  pieces  of  wood  e  e  are  fixed  to  the 
legs,  by  which  the  instrument  is  held,  to  prevent  any  inconvenience 
to  the  hand.  Under  this  last  forceps,  is  still  another,  made  of 
iron,  which  can  be  used  for  a  variety  of  operations,  and  which  is 
not  solely  confined  to  this  application.  Substances  to  be  held 
very  firmly  are  placed  between  the  points.  It  has  a  button  d  d, 
with  a  steel  spring  d  e,  to  prevent  the  forceps  from  opening  by 
the  sliding  back  of  the  button. 

Microscope. — A  plano-convex  microscope,  with  two  lenses  of 
different  magnifying  powers,  is  often  useful  in  minute  analysis, 
and  one  is  represented  in  Fig.  496,  which  is  made  to  fit  in  a  small 


INSTRUMENTS   USED   IN   BLOWPIPE   ANALYSIS. 


587 


receptacle.  By  its  aid,  the  minute  structure  of  bodies,  and  fine 
colors  imparted  to  the  fluxes  or  to  charcoal,  which  often  deceive 
the  naked  eye,  are  examined. 

Fig.  496. 


Charcoal  Borer. — A  conical  tube  of  tinned  iron,  with  the 
margin  filed  to  -a  sharp  edge,  for  making  cavities  in  the  charcoal 
support,  is  often  made  to  occupy  a  place  in  blowpipe  apparatus. 
It  answers  very  well  as  a  case  to  contain  a  vial,  as  shown  in  the 
figure  above.  Another  form  of  charcoal  borer  is  presented  in  the 
annexed  drawing,  Fig.  497.  "  It  is  a  four-sided  pyramid  of  hard- 
Fig.  497. 


ened  steel,  with  its  sides  filed  away,  so  as  to  give  it  the  form  of 
a  double  chisel  crossing  at  right  angles."     It  is  used  for  boring  a 
round  hole  in  the  charcoal,  by  pressing  it  against  the  latter  and 
turning  it  upon  its  axis  until  the  cavity  is  sufficiently  deep. 
A  pair  of  cutting  pliers  are  used  to  clip  off  small  particles  of 

Fig.  498. 


minerals  and  pieces  of  a  metal  or  alloy  for  examination,  and  for 
many  other  purposes  which  will  suggest  themselves  to  the  expe- 


588  INSTRUMENTS   USED   IN   BLOWPIPE   ANALYSIS. 

riinenter.     A  clasp  is  attached  to  the  handles  for  the  purpose  of 
keeping  them  forcibly  closed. 

Hammer    and    Anvil. — A    polished    hammer    of    hardened 
steel,  Fig.  499,  with  a  square,  even  surface  at  one  end,  and  the 

Fig.  499. 


other  terminating  in  an  edge  with  sharp  corners,  is  a  very  neces- 
sary implement.  The  flat  surface  is  very  applicable  for  flattening 
globules  of  reduced  metals,  and  the  edge  for  breaking  off  small 
pieces  of  minerals.  Very  small  fragments  can  be  broken  off 
without  doing  any  injury  to  the  remaining  portion,  which  is  often 
kept  as  a  specimen. 

A  necessary  accompaniment  to  the  hammer  is  the  anvil,  which 

is  represented  by  Fig.  500,  in  a  most 

lg'       convenient  and  compact  form.     It  is 

made  of  steel,  and  is  usually  about 
three  inches  long,  one  inch  in  thick- 
ness, and  five-eighths  of  an  inch  in 
breadth,  and  any  one  of  its  surfaces 
can  be  used.  The  substance  to  be 

broken  up,  or  the  metallic  globule  to  be  flattened  out,  is  enclosed 
In  thin  paper,  and  having  been  placed  upon  the  anvil,  is  struck 
with  the  hammer  until  the  proper  effect  is  produced.  If  the  sub- 
stance is  reduced  to  powder,  the  paper  prevents  any  of  it  from 
being  scattered  or  lost. 

Mortar  and  Pestle. — These  implements,  made  of  agate,  are 
of  small  size,  and  have  been  described  at  page  92.  They  should 
be  hard  and  perfectly  free  from  holes  and  cracks,  or  they  will 
be  liable  to  fracture,  and  to  the  filling  up  of  their  crevices 
with  the  powdered  materials, — much  to  the  detriment  of  future 
operations. 

Electroscope  and  Magnetic  Needle  Case. — A  cylindrical 
wooden  box  is  used  to  contain  Hatiy's  electroscope  and  a  mag- 
netic needle. 


INSTRUMENTS    USED   IN   BLOWPIPE   ANALYSIS.  589 

The  former  consists  of  the  hair  of  a  cat,  insulated  by  being 
inserted  in  sealing-wax  poured  into  the  bore  of  a  small  glass  tube. 
This  tube  is  fastened  in  a  wooden  screw,  which  closes  at  one  end 
of  the  case.  It  is  so  delicate  that  a  very  small 
quantity  of  electricity  is  discovered  by  its  aid. 
On  bringing  it  near  to  an  excited  body,  it  is  at- 
tracted by  it ;  but  if  negative  electricity  is  deve- 
loped in  it,  by  rubbing  or  drawing  it  rapidly 
through  the  fingers,  and  it  is  then  brought  in 
proximity  to  the  excited  body,  it  will  be  attracted 
or  repelled  in  accordance  with  the  existence  in  that  body  of  posi- 
tive or  negative  electricity.  In  the  screw  at  the  other  end  (each 
one  serving  as  a  stand),  is  fixed  a  similar  tube  and  sealing-wax  to 
insulate  a  small  steel  pin,  which  supports  a  magnetic  needle  con- 
tained in  the  box.  The  needle  is  mounted  with  an  agate  cup  to 
prevent  friction  as  much  as  possible,  when  suspended  on  the  point 
of  the  pin.  In  this  condition,  it  is  used  to  indicate  the  presence 
of  iron  when  it  exists  in  a  mineral  in  an  appreciable  quantity, 
and  also  the  magnetic  condition  of  iron  ores.  Minerals,  before 
and  after  being  submitted  to  the  action  of  the  blowpipe,  should 
be  examined  in  regard  to  these  properties. 

Steel  Magnet. — This  is  employed  in  the  mode  recommended 
by  Haiiy  to  ascertain  whether  the  slightest  trace  of  magnetic 
force  exists  in  minerals,  and  consequently  whether  the  metals  in 
which  that  force  exists  are  present.  The  experiment  is  thus  per- 
formed. The  magnet  is  placed  at  a  small  distance  from  a  sus- 
pended magnetic  needle,  its  north  pole  being  directed  towards 
that  of  the  needle ;  it  is  then  gently  moved  around  the  needle 
until  the  latter  takes  a  position  at  right  angles  to  its  former  place, 
owing  to  the  repulsion  of  the  same  kind  of  magnetism.  This  re- 
pulsion, and  the  force  of  terrestrial  attraction,  which  tends  to 
make  the  needle  return  to  its  former  direction,  now  hold  the  needle 
exactly  balanced  between  them,  so  that  the  smallest  disturbing 
magnetic  force  moves  it  out  of  its  place.  In  this  way,  an  amount 
of  magnetic  influence  may  be  detected,  which  would  not  be  suffi- 
cient to  affect  the  needle  in  its  ordinary  state.  In  performing 
this  experiment,  care  must  be  taken  not  to  excite  electricity  in 
the  mineral  by  friction,  as  that  force  might  affect  the  result  more 
or  less. 


590  INSTRUMENTS    USED    IN    BLOWPIPE   ANALYSIS. 

A  knife  of  good  hardened  steel  is  used  for  trying  the  compara- 
tive hardness  of  metallic  bodies  and  minerals  generally.  It  may 
be  used  as  a  charcoal  borer,  and  if  well  magnetized  can  be  sub- 
stituted for  the  magnet.  The  point  is  used  to  take  up  the  fluxes 
before  mixing  them  in  the  palm  of  the  hand  with  the  mineral 
which  has  been  pulverized  for  examination. 

Files  are  convenient  for  detaching  small  particles  of  a  metal 
which  is  to  be  investigated,  cutting  glass  tubes,  and  for  trying 
the  hardness  of  bodies.  They  may  be  of  different  shapes,  and 
should  be  kept  clean,  and  out  of  the  reach  of  corrosive  vapors. 

An  Edulcorator  or  spritz,  Fig.  428.  This  is  used  to  wash  the 
charcoal  from  the  reduced  metal.  It  is  necessary  to  be  very 
cautious  in  doing  this  when  the  metal  is  small  in  quantity,  as  the 
force  of  the  jet  may  carry  the  latter  away  with  the  charcoal.  A 
pipette  or  dropping-tube,  made  by  drawing  out  in  the  flame  of  a 
candle  or  spirit-lamp  one  end  of  a  glass  tube  to  a  small  opening, 
can  be  used  with  less  danger.  The  separation  will  be  facilitated, 
by  reducing  to  powder,  in  the  agate  mortar,  for  the  charcoal 
adhering  to  the  piece  of  metal,  as  the  globule,  if  malleable,  will 
be  thus  slightly  flattened  and  made  more  distinctly  visible. 

Small  capsules  of  porcelain,  or  watch  glasses,  are  useful  as 
temporary  receptacles  for  the  results  of  the  experiments ;  such  as 
specimens  of  reduced  metal,  the  colored  beads,  &c.,  and  for 
keeping  separate  different  fragments  of  the  minerals  to  be  in- 
vestigated. 

A  small  pair  of  scissors,  a  pair  of  small  tongs  for  holding  cru- 
cibles, &c.,  over  the  spirit-lamp,  a  small  capsule  of  platinum,  a 
touchstone  with  needles  of  gold,  and  alloys  of  different  standards 
for  trying  the  fineness  of  gold,  will  each  be  occasionally  required. 

Fig.  002. 


Sox  containing  the  Reagents. — As  it  is  necessary  to  have  the 
fluxes  always  ready  for  use,  Gahn  contrived  a  convenient  and 


THE   REAGENTS.  591 

portable  box  for  the  purpose,  which  is  seen  in  Fig.  502.  It  is  8J 
inches  long,  Iy3g  broad,  1  inch  in  height,  and  is  divided  into  nine 
compartments  to  receive  the  different  reagents.  Each  division  has 
a  lid  nicely  closing  its  particular  box,  so  as  to  prevent  any  one 
substance  from  becoming  mixed  with  the  others.  A  common  lid 
closes  over  these  smaller  ones,  and  is  fastened  to  the  box  by  two 
hooks.  The  cross  pieces,  which  are  permanently  fixed  to  the 
large  lid,  fit  into  spaces  between  the  second  and  third  lids  from 
each  end,  and  serve  to  make  them  more  secure. 

The  Reagents. — The  reagents,  which  must  all  be  chemically 
pure,  are  the  following : 

Carbonate  of  Soda,  commonly  called  soda,  which  is  much  used 
to  detect  the  presence  of  silica,  to  assist  the  reduction  of  metallic 
oxides,  arid  generally,  to  determine  whether  a  body  unites  with  it 
to  the  production  of  a  fusible  compound. 

Cyanide  of  Potassium. — This  substance  being  very  deliques- 
cent, should  be  kept  as  free  as  possible  from  contact  with  humid 
air,  and  had  better  be  placed  in  a  small,  tightly  corked  test-tube, 
which  may  have  its  place  in  one  of  the  small  compartments  of 
the  box. 

As  a  blowpipe  reagent,  cyanide  of  potassium  is  highly  useful ; 
its  action  is  indeed  extraordinary.  Substances  like  peroxide  of 
tin,  sulphuret  of  tin,  &c.  &c.,  which  for  their  reduction  with  car- 
bonate of  soda,  require  rather  a  strong  flame,  are  reduced  with 
the  greatest  facility  when  cyanide  of  potassium  is  used.  In  blow- 
pipe experiments  we  always  use  a  mixture  of  equal  parts  of  car- 
bonate of  soda  and  of  cyanide  of  potassium,  since  the  latter  alone 
fuses  too  easily.  This  mixture,  besides  its  more  powerful  action, 
has  another  advantage  over  carbonate  of  soda :  it  is  with  extreme 
facility  imbibed  by  the  porous  charcoals,  so  that  the  purest 
metallic  globules  are  obtained. 

Biborate  of  Soda. — This  salt,  which  is  commonly  called  borax, 
is  used  to  facilitate  the  fusion  of  very  many  substances.  When 
melted  with  the  metallic  oxides,  its  bead  assumes  a  great  variety 
of  colors,  which  furnish  excellent  indications  of  the  presence  of 
the  metals. 

Phosphate  of  Soda  and  Ammonia. — This  substance,  called 
also  microcosmic  salt,  phosphorus  salt,  and  fusible  flux,  is  of  very 
general  application,  and  as  it  dissolves  most  of  the  metallic 


592  THE    REAGENTS. 

oxides  with  great  readiness,  the  colors  produced  in  its  bead  are, 
if  possible,  more  brilliant  and  characteristic  than  those  made 
with  borax. 

Nitrate  of  Potassa,  or  saltpetre,  is  used  to  assist  in  the  oxida- 
tion of  metals,  as  it  yields  up  its  oxygen  very  readily  when 
exposed  to  heat. 

Bisulphate  of  Potassa  in  solution,  is  used  to  indicate  lithia, 
boracic  acid,  nitric  acid,  fluohydric  acid,  bromine,  and  iodine ; 
and  also  for  the  separation  of  baryta  and  strontia  from  other 
earths  and  metallic  oxides. 

Vitrified  Boracic  Acid  (glass  of  borax),  is  used  to  detect  the 
presence  of  phosphoric  acid ;  also  small  portions  of  copper  in 
alloys  of  lead. 

Fluoride  of  Calcium  (fluor  spar),  when  mixed  with  bisulphate 
of  potassa,  serves  to  detect  lithia  and  boracic  acid.  Alone,  it  is 
a  test  for  gypsum. 

Sulphate  of  Lime,  or  gypsum,  in  the  form  of  plaster  of  Paris, 
is  sometimes  used  as  a  reagent  with  fluoride  of  calcium. 

Nitrate  of  Cobalt. — This  very  valuable  test  is  used  in  a  some- 
what concentrated  solution. 

Alumina  heated  in  the  oxidating  flame,  after  being  moistened 
by  a  drop  or  two  of  this-  solution,  acquires  a  beautiful  pale  blue 
color,  magnesia  a  rose-red  tint,  and  zinc  a  bright 
Figj303,  green.  The  solution  is  contained  in  a  phial  similar  to 
the  one  represented  in  Fig.  503.  The  glass  stopple, 
tapering  to  a  point,  descends  into  the  solution,  so  that 
on  withdrawing  it,  a  small  quantity  adheres  to  its  ex- 
tremity. Berzelius  uses  a  cork  stopple  with  a  platinum 
wire  flattened  out  in  the  form  of  a  spoon,  the  end  of 
which  is  immersed  in  the  solution.  The  phial  may  be 
of  such  a  size  as  to  be  conveniently  received  in  the  charcoal 
borer,  Fig.  496.  Oxalate  of  cobalt  may  be  made  to  take  its 
place,  and  as  it  is  used  in  powder,  it  is  often  of  more  convenient 
application. 

Nitrate  of  Nickel  in  solution,  or  Oxalate  of  Nickel  in  powder. 
The  oxide  of  nickel  gives  a  brown  color  to  soda  glass,  while  pot- 
ash, if  melted  with  a  substance  containing  it,  acquires  a  bluish- 
purple  color.  A  bottle  similar  to  the  one  just  described  may 
contain  the  solution  of  the  nitrate. 


THE   REAGENTS.  593 

Lead,  very  pure,  and  especially  free  from  silver,  is  used  in 
cupellation. 

Bone  ashes  are  employed  in  cupelling  metals  containing  gold 
and  silver,  and  some  of  the  ores.  The  cupels  are  prepared  by 
moistening  a  small  quantity  of  the  ashes,  mixed  with  a  little  soda- 
salt  to  make  it  coherent,  and  by  kneading  the  mass  in  the  palm 
of  the  left  hand  to  the  consistence  of  a  stiff  paste.  A  cylindrical 
hole  made  in  a  piece  of  charcoal  is  then  filled  with  the  paste,  and 
after  the  surface  is  smoothed  with  the  small  agate  pestle,  a  slight 
depression  is  made  in  the  centre,  sufficiently  large  to  hold  the 
metal  or  mineral  to  be  cupelled,  together  with  a  small  quantity 
of  the  proof  lead.  The  cupel  is  slowly  dried  by  heating  it  care- 
fully in  a  stove  or  over  the  flame  of  a  spirit  lamp.  The  assay 
with  the  lead  is  then  placed  on  the  cupel  and  submitted  to  the 
action  of  the  exterior  or  oxidating  blowpipe  flame.  By  the  in- 
fluence of  this,  the  lead  is  oxidized,  and  the  fused  litharge  so 
formed,  is  absorbed  by  the  bone  ashes,  while  the  silver  or  gold  is 
left  behind  in  the  form  of  a  brilliant  globule ;  which,  before  its 
complete  purification,  exhibits  the  iridescence  formerly  described 
under  CUPELLATION.  Plattner  describes  a  convenient  instrument 
for  making  the  cupels. 

Oxide  of  Copper  is  used  for  the  purpose  of  detecting  chlorine. 

Silicic  Acid,  when  melted  into  a  fusible  glass  with  soda,  is  a 
test  for  sulphur  or  sulphuric  acid.  The  assay  must,  however,  not 
contain  it. 

Silver,  in  the  form  of  wire  or  foil,  is  made  use  of  for  ascer- 
taining the  presence  of  sulphuret  of  potassium,  or  any  other 
soluble  sulphuret. 

Tin  Foil  sometimes  assists  in  the  reduction  of  metallic  oxides, 
which  are  dissolved  in  a  bead  of  one  of  the  fluxes,  and  by  its  use 
we  sometimes  get  a  more  satisfactory  result  than  is  obtained  with- 
out it.  For  instance,  when  a  small  quantity  of  copper  is  dissolved 
in  a  bead  of  borax,  or  of  microcosmic  salt,  and  the  glass  is  treated 
in  the  reducing  flame,  it  sometimes  becomes  ruby-red  and  opaque. 
But  if  the  amount  of  copper  is  so  small  that  the  reducing  flame 
cannot  produce  this  result,  a  little  tin  added  to  the  bead,  and 
heated  with  it,  makes  the  proper  appearance  evident  immediately 
upon  its  cooling. 

Iron  wire,  which  is  generally  that  metal  in  its  purest  state, 

38 


594  BLOWPIPE   TABLE. 

precipitates  some  other  metals  from  the  different  fluxes,  or  sepa- 
rates therefrom  sulphur  and  the  fixed  acids.  It  is  also  used  to 
reduce  phosphoric  acid  to  phosphorus,  which,  combining  with  iron, 
forms  a  white  brittle  metallic  globule,  the  phosphuret  of  iron. 

Besides  the  above-mentioned  tests,  it  is  proper  to  have  Formate 
of  Soda,  which,  when  anhydrous,  is  used  to  detect  arsenic  in  oxide 
of  antimony.  Test  papers  colored  with  litmus,  Brazil  wood,  and 
turmeric,  are  also  convenient. 

The  substances  mentioned  in  the  foregoing  list  as  reagents, 
are  all  of  those  which  are  essential  to  the  completeness  of  the 
blowpipe  apparatus.  While,  however,  occasions  may  arise  for 
the  use  of  any  or  all  of  them,  the  great  majority  of  examinations 
with  the  blowpipe  can  be  made  with  the  aid  of  but  a  few,  and  the 
possession  of  the  first  four  or  five  upon  our  list,  with  the  fluid 
nitrate  of  cobalt  and  the  metals  referred  to,  may  be  considered 
as  quite  enough  to  make  the  manipulator  competent  to  pursue 
ordinary  investigations. 

Blowpipe  Table. — In  the  laboratory  all  the  instruments  essen- 
tial to  the  expedition  of  blowpipe  analysis  are  placed  within  con- 
venient reach  of  the  operator.  For  this  purpose  Gahn's  table, 

Fig.  5(J4. 


which  has  drawers  both  in  the  side  and  front,  will  be  found  very 
useful.  The  side  drawers  are  shown  in  Fig.  504,  drawn  out  from 
their  usual  position.  The  right  hand  drawer  contains  the  appa- 


BLOWPIPE   TABLE.  595 

ratus  most  frequently  used,  and  the  left  that  which  is  less  often 
required.  The  lamp,  blowpipe,  fuel,  wick,  and  other  necessaries 
of  a  rougher  kind,  occupy  those  in  front. 

The  drawers  are  fitted  with  receptacles  for  each  and  every 
article,  so  that  they  may  rest  securely,  when  moved ;  and  they 
can  therefore  he  readily  formed  into  a  travelling  case.  Chests, 
however,  for  this  purpose,  are  specially  constructed  with  great 
regard  to  economy  of  space  and  number  of  conveniences.  Those 
made  by  Lingke,  comprise,  in  a  case  of  about  twelve  inches 
square,  and  admirably  arranged  with  drawers  and  apartments,  all 
the  implements  and  accessories  for  quantitative  as  well  as  quali- 
tative blowpipe  assays,  including  a  compact  and  very  delicate 
balance  with  weights. 

Having  fulfilled  our  duty  of  describing  the  more  practical 
points  of  blowpipe  operations,  we  refer  the  reader,  for  all  other 
necessary  information,  to  the  comprehensive  treatises  of  Berzelius 
and  Plattner,  both  of  which  have  been  translated  into  English, 
the  first  by  Whitney  and  the  second  by  Muspratt. 

The  annexed  tables  will  also  serve,  conveniently,  both  as  a 
guide  and  for  reference,  in  practical  exercises.  For  testing  by 
them  observe  the  following  directions : 

Fuse  a  globule  of  microcosmic  salt  on  platinum  wire ;  add  a 
small  quantity  of  the  substance  to  be  tested,  and  again  heat  to 
redness  in  the  oxidizing  flame  ;  observe  the  color  of  the  globule, 
and  allow  it  to  cool,  and  again  note  its  color.  The  substance 
may  thus  be  referred  to  one  of  six  classes.  If  the  globule  is 
colorless,  add  a  further  quantity  of  the  substance  to  be  tested, 
and  treat  as  before,  in  order  to  ascertain  if  the  globule  will  become 
opaque  on  saturation.  Then  heat  the  same  globule  in  the  redu- 
cing flame,  and  again  note  its  color.  Repeat  the  operations  with 
a  globule  of  borax,  and,  if  necessary,  apply  the  special  tests  given 
under  the  head  of  Remarks  to  Individualize. 


596 


TABLE  FOR  TESTING  BY  THE  BLOWPIPE. 


REMARKS. 

Compounds  containing  chromium,  when 
fused  with  nitre  and  potash  in  a  silver 
crucible,  yield  a  yellow  mass,  containing 
chromic  acid. 
Compounds  containing  copper,  when  fused 
with  soda  on  charcoal,  yield  metallic  cop- 
per. Copper  is  malleable,  and  red  in  color; 
is  acted  upon  by  nitric  acid,  giving  a  solu- 
tion which  is  turned  blue  by  an  excess  of 
ammonia. 

Compounds  containing  manganese,  when 
fused  with  nitre  and  potash  (see  2),  yield 
a  bright  green  mass  (mineral  chameleon). 

On  charcoal  are  only  partially  reduced; 
with  soda,  on  ditto,  fuse,  and  are  absorbed. 

Compounds  containing  silver,  on  charcoal 
in  R.  F.,  alone  or  with  soda,  are  easily 
reduced.  Silver  is  easily  fused,  silvery 
white  in  color,  malleable,  and  not  oxidiz- 
able,  B.B.;  is  soluble  in  nitric  acid,  and 
the  sol.  yields  a  white  curdy  precipitate 
with  hydrochloric  acid. 

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Compounds  of  mercury,  when  heated  in  a 
tube  with  tin  or  iron  filings,  yield  a  gray 
sublimate  of  metallic  mercury,  which,  when 
examined  by  a  lens,  is  seen  to  consist  of 

minute  globules. 
Arsenical  compounds,  when  heated  in  a 
tube  with  black  flux  or  cyanide  of  potas- 

sium,  yield  a  steel-gray  mirror-like  subli- 
mate of  metallic  arsenic.  This,  when 

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aceous odor,  and  yields  a  sublimate  of  ar- 
senious  acid,  crystallized  in  brilliant  co- 

lorless octohedra. 

Are  easily  reduced  on  charcoal,  with  soda, 
in  R.F.  Metal  very  fusible,  malleable, 
silvery  white  in  color;  oxidizes  in  O.F., 
and  gives  a  non-volatile  white  oxide  coat- 

iw«T  */<e  surface  of  the  fused  metal;  areola, 
none. 

Is  not  reduced  on  charcoal. 

Compounds  of  alumina,  when  moistened 
with  nitrate  of  cobalt,  give  a  beautiful  blue 
enamel  before  the  blowpipe. 
Compounds  of  soda  communicate  a  bright 
yellow  color  to  the  blowpipe  flame. 
Compounds  of  lithia  color  the  flame  red. 

if  no  soda  is  present. 
Compounds  of  potash  color  the  flame  pale 
lilac,  or  violet,  if  no  soda  is  present. 

Compounds  of  ammonia,  when  heated  with 
lime  or  potash,  give  off  ammoniacal  gas. 

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GLASS-BLOWING.  601 

CHAPTER  XXX. 

GLASS-BLOWING. 

THE  ability  to  work  glass  over  the  lamp  or  blowpipe-flame  is  a 
very  desirable  accomplishment  for  the  chemist,  as  it  enables  him 
to  fashion  for  himself,  and  in  accordance  with  his  own  judgment, 
such  micro-apparatus  as  is  constantly  in  demand  during  experi- 
mental research.  The  inconvenience  and  expense  of  having  a 
large  stock  of  delicate  glass  instruments  always  at  hand,  and  the 
difficulty  of  obtaining  such  at  all  times,  especially  in  localities 
distant  from  the  cities,  render  instruction  in  the  art  doubly  de- 
sirable. On  these  accounts,  we  think  it  proper  to  devote  a  chap, 
ter  to  a  few  illustrations  of  the  processes  by  which  tubes  are  bent, 
closed,  rounded,  widened,  and  drawn  out,  and  by  which  bulbs  are 
blown  and  joints  sealed. 

The  two  principal  pieces  of  apparatus  required  are  a  lamp  and 
a  table  blowpipe.  The  latter,  as  well  as  its  management,  have 
already  been  written  of  at  page  69.  The  former,  known  as  Dan- 
ger's "  Glass-blower's  Improved  Lamp,"  of  form  shown  by  Fig. 
505,  is  of  sheet  brass,  and  rests  upon  a  tray  designed  for  the 

Fig.  505. 


reception  of  any  overflow  of  oil.  These  lamps  are  fitted  with  an 
arrangement  by  which  the  wick  may  be  raised  or  lowered,  and 
the  flame  consequently  enlarged  or  diminished  as  desired:  an 
accompanying  hood,  or  short  conical  chimney  over  the  burning 
wick,  serves  to  increase  the  heat  and  to  protect  the  eyes  from  the 
smoke  and  flame. 


602  THE   TABLE. 

The  wick  may  be  made  of  common  candle-wick,  divided  into 
lengths  of  proper  dimensions,  and  stranded  together,  so  as  to 
form  a  diameter  of  about  three-fourths  of  an  inch.  This  bunch 
is  placed  in  that  part  of  the  lamp  intended  as  its  receptacle,  and 
should  only  protrude  above  the  oil  about  the  third  of  an  inch. 
It  should  be  kept  constantly  supplied  with  oil  or  fat,  and  free 
from  "snuff"  by  frequent  trimming.  To  obtain  the  highest  pos- 
sible heat  from  the  lamp,  the  vent-hole  in  the  nozzle  c  of  the 
blast  table  must  be  very  small  compared  with  the  capacity  of  the 
wind  chest,  and  when  it  is  desired  to  lessen  the  power  of  its  flame, 
as  may  be  necessary  in  the  heating  of  small  tubes,  the  force  of 
the  blast  must  be  diminished. 

The  fuel  may  be  olive,  lard,  sperm,  or  tallow  oil ; — the  latter, 
however,  being  preferable  on  account  of  its  giving  a  hotter  flame. 
In  case  of  the  absence  of  a  lamp  of  this  sort,  any  common  me- 
tallic vessel,  of  proper  size,  may  be  fitted  for  use,  upon  the  blow- 
pipe-table, by  training  up  upon,  and  allowing  to  overhang  its 
side,  a  thick  bunch  of  wick.  This  may  be  kept  in  place,  and  its 
flame,  at  the  same  time,  be  prevented  from  descending  too  far, 
by  encircling  it  with  a  tin  or  other  metallic  tube,  or  a  coil  of  wire, 
which  may  be  temporarily  connected  with  the  sides  of  the  vessel, 
so  as  to  answer  all  the  intentions  of  support  and  the  conduction 
off  of  the  excess  of  heat. 

If  the  experimenter  cannot  have  access  to  a  properly  made 
blowpipe  table,  he  may,  in  a  very  short  time,  construct  a  substi- 
tute himself,  which,  however  rough,  will  enable  him  to  carry  on 
nearly  all  the  operations  of  glass-blowing.  A  hollow  reed  or 
piece  of  cane-angle,  about  a  foot  in  length,  may  be  firmly  fixed 
in  a  circular  hole,  drilled  near  the  edge  of  a  common  table,  and 
which  is  just  large  enough  to  admit  and  hold  it  firmly  in  its  place. 
This  may  have  adapted,  by  means  of  cement,  plaster,  or  putty, 
to  its  upper  end,  a  nozzle  of  metal,  or  of  glass  drawn  out  to  the 
proper  sized  orifice,  or  one  made  of  a  piece  of  tobacco-pipe  of  the 
requisite  calibre.  A  bladder  of  the  largest  size,  or  bag  of  caout- 
chouc, furnished  with  two  openings  upon  the  same  part  of  its 
circumference,  is  now  firmly  attached  to  the  bottom  of  this  tube, 
in  one  of  which  a  similar  piece  of  reed,  long  enough,  however,  to 
reach  from  the  operator's  knees — while  sitting — to  his  mouth, 
having  been  inserted  and  tied  into  the  other  opening.  That  end 


IMPLEMENTS. 


603 


of  this  last-mentioned  tube  which  is  within  the  bladder,  should 
be  provided  with  a  valve,  like  that  of  a  cupping-glass,  made  by 
placing  loosely  over  it,  a  long  strip  of  oiled  silk,  of  the  diameter 
of  the  tube,  folding  the  ends  upon  the  body  of  the  reed  and 
tying  them  firmly  to  it  by  waxed  thread.  This  valve  admits  the 
passage  of  air  into  the  receptacle,  but  will  not  allow  its  return 
through  the  same  orifice,  so  that  pressure  upon  the  bladder  will 
compel  its  exit  through  the  nozzle  of  the  tube  which  is  fixed  in 
the  table.  If,  then,  the  operator,  sitting  near  the  table,  with  the 
bladder  hanging  between  his  knees  and  the  loose  tube  fixed  in 
his  mouth,  inflates  the  former,  and  then  presses  upon  it  uniformly 
with  his  knees,  a  continuous  current  is  expelled  from  the  nozzle 
upon  the  flame  of  the  wick  placed  directly  above  it.  A  repeti- 
tion of  the  inflation  only  becomes  necessary  when  the  bladder  is 
nearly  emptied  of  its  contained  air.  The  inflation  of  this  home- 
made apparatus  is  scarcely,  if  at  all  fatiguing ;  and  it  gives  to 
the  glass-blower  the  unincumbered  use  of  both  his  hands.  Russia 
lamps,  and  similar  implements,  described  in  Chapter  XI,  may,  in 
many  cases  of  glass-blowing,  be  substituted  for  the  blast-table 
and  Danger  lamp. 

Fig.  506. 


The  position  of  the  jet  upon  the  top  of  the  table,  and  that  of 
the  operator  before  it,  are  shown  in  the  annexed  drawing. 


604 


IMPLEMENTS. 


When  it  is  desired  to  use  the  gas  flame,  the  straight  jet  and 
Argand  burner,  as  is  shown  in  the  annexed  drawing,  are  em- 
ployed. It  is  still  better,  in  ordering  a  blast-table,  to  have  pre- 
pared a  movable  jet,  with  ball  and  socket  joint,  suitable  for  giving 
the  flame  a  horizontal  or  vertical  direction,  as  may  be  required. 

The  other  implements  are  an  iron  piercer  with  wooden  handle, 
Fig.  507,  a  cone  of  biscuit-ware  or  soap-stone,  Fig.  508,  for 


Fig.  507. 


Fig.  503. 


Fig.  509. 


widening  the  necks  of  tubes,  a  small  pair  of  brass  tongs,  Fig. 
509,  for  fashioning  bulbs,  &c.,  a  small  piece  of  smooth  hoop-iron, 
styled  the  marver,  a  hardened  cast-steel  knife,  and  one  or  two 
three-cornered  files  for  cutting  tubes  and  rods. 

In  addition  to  the  above,  the  table  should  be  supplied  with  a 
stock  of  tubes  and  rods,  of  assorted  diameters,  and  made  of  glass 
free  from  lead.  They  should,  moreover,  be  very  uniformly 
regular  throughout,  and  exempt  from  flaws  or  striae. 

To  prevent  the  table  from  being  incumbered  and  uncleanly,  the 


Fig.  510. 


Fig.  511. 


long  tubes  should  be  kept  in  a  rack  like  that  shown  by  Fig.  510, 
and  the  shorter  pieces  in  one  as  presented  by  Fig.  511. 


CUTTING   OP   GLASS.  605 

Before  commencing  operations,  the  wick  must  be  evenly 
trimmed  and  parted  in  the  middle,  so  that  when  the  jet  is  placed 
opposite  in  the  rear,  and  in  proper  relation,  it  may  drive  the 
flame*  forcibly  in  advance,  but  not  of  too  great  length,  else  it  will 
become  smoky. 

Tubes  can  very  readily  be  severed,  or  divided  into  lengths,  by 
scratching  them  with  a  file,  and  breaking  asunder  as  at  Fig.  519. 
For  large  tubes,  the  scratch  must  extend  entirely  around  the 
circumference. 

Vessels  of  larger  diameters,  such  as  necks  of  retorts,  and  the 
like,  require  the  use  of  a  diamond  spark.  According  to  Mr.  Nas- 
myth,  coke  has  the  property  of  cutting  glass,  and  can  very  well 
be  substituted  for  the  diamond. 

When  the  scratch  of  the  file  is  insufficient  to  effect  a  smooth 
division,  it  must  be  moistened  and  then  traced  with  a  heated  wire 
or  pastile.  A  heated  wire  will  also  divert  a  crack  in  a  glass  ves- 
sel to  any  desired  direction. 

The  tubes  or  rods,  previously  divided  into  the  required  length, 
should  always  be  wiped  perfectly  dry  before  being  subjected  to 
the  action  of  the  flame,  and  then  carefully  and  gradually  heated, 
the  uniform  diffusion  of  the  heat  being  effected  by  keeping  them 
revolving ; — these  precautions,  which  are  always  to  be  observed, 
prevent  breaking  from  sudden  and  unequal  heating.  After  being 
heated,  they  must  be  removed  gradually  from  the  fire,  and  laid 
upon  a  piece  of  charcoal,  so  as  to  become  annealed,  as  it  were, 
by  gradual  cooling. 

The  most  simple  and  easily  performed  of  all  the  operations  of 

Fig.  512. 


glass-blowing,  is  the  rounding  of  edges,  which  is  readily  done  by 
heating  them  to  softness  in  the  flame  during  constant  revolution 


606  TUBES  CEMENTED — TUBES  BENT. 

of  the  tube  between  the  thumb  and  three  fingers,  which  support 
it.  This  operation,  by  which  the  edges  of  tubes  and  rods  are 
smoothed,  is  also  preliminary  to  that  of  widening  the  mouth  of 
a  tube,  a  test-tube  for  example,  which  is  done  by  spreading  it 
while  hot,  as  shown  in  Fig.  512,  by  means  of  the  iron  piercer, 
or,  better,  the  biscuit  cone,  either  of  them  being  previously 
warmed,  and  then  carried  round  the  opening  with  an  outward 
pressure. 

Tubes  Cemented. — Tubes  or  rods  are  also  cemented  together 

by  softening  their  ends  and  blowing  gently  through  them  at  the 

moment  of  junction.    Care  must  be  taken 

Fig.  513.  to  hold  them  firmly  and  perfectly  even, 

^^-jjifr-     .L,jj-.'w    as  S^own  i*1  -Fig-  513,  and  to  retain  hold 
;.--J||'  of  the  joined  tube  until  it  has  entirely 

cooled,  else  it  may  bend  by  its  own  weight 
at  the  heated  part,  and  thus  become  crooked. 

If  the  tubes  to  be  cemented  are  of  unequal  diameters,  the  wider 
one  must  be  closed  at  its  end,  then  heated  in  the  flame  and 
quickly  blown  into  a  thin  bulb,  as  shown  by  A,  Fig.  514.  This 

bulb  is  then  broken  off  so  as  to 
Fig<  514>  leave  only  a  shoulder  at  the  mouth 

B.  This  being  done,  the  end  of 
the  small  tube  is  next  blown  in 
the  same  manner,  as  at  c,  and  the 
two  shoulders  are  then  to  be  ce- 
mented as  before  directed. 

Kods  are  cemented  together  by  partially  fusing  their  ends  and 
bringing  them  carefully  together,  and  pressing  them  until  they 
adhere.  The  welding  is  then  completed  by  heating  the  new  joint, 
during  which  process,  in  order  to  impart  shape,  the  rods  must  be 
kept  rotating,  and  be  alternately  drawn  out  and  brought  together, 
until  the  junction  is  as  smooth  and  uniform  as  any  other  part  of 
the  surface. 

Tubes  Bent. — Very  small  tubes  can  be  bent  over  the  spirit 
lamp,  Fig.  151 ;  but  larger  ones  require  the  force  of  the  blow- 
pipe-flame to  heat  them.  The  operation  of  bending  consists  in 
heating  the  tube  to  dull  redness,  about  an  inch  on  either  side 
beyond  the  point  of  the  intended  curve,  by  revolving  it  in  the 
flame,  and  just  at  the  commencement  of  softening,  in  making  an 


DRAWING   OUT, 


607 


angle,  by  bending  it  dexterously,  but  very  gradually,  in  the  de- 
sired direction  until  it  assumes  the  required  form.  In  order  to 
prevent  a  wrinkled,  and  consequently  very  fragile  elbow,  Fig.  515, 
it  is  necessary  that  the  operation  of  bending  shall  be  accomplished 
by  progressive  steps,  as  illustrated  by  Fig.  517.  Closing  the 


Fig.  515. 


Fig.  516. 


Fig.  517. 


tube  at  one  end,  and  blowing  gently  into  the  other,  during  flexion, 
so  as  to  produce  internal  pressure,  will  also  counteract  any  ten- 
dency to  malformation. 

Drawing  Out. — When  a  tube  is  to  be  drawn  out,  either  as  pre- 
liminary to  further  working,  or  in  the  preparation  of  nozzles  for 
washing-bottles,  or  other  purposes,  one  of  the  proper  size  is  taken, 
at  the  ends,  between  the  thumb  and  index  of  each  hand,  and 
along  its  length  with  the  other  fingers,  and  kept  revolving  gradu- 
ally over  the  flame  until  it  becomes  red,  and  commences  to  soften 
at  the  heated  part.  It  is  then  taken  from  the  fire  and  drawn 
apart,  as  shown  in  Fig.  518.  In  this  way  also  stirring-rods  are 

Fig.  518. 


pointed,  and  when  the  tips  of  either  tubes  or  rods  thus  wrought 
are  to  be  smoothed,  it  is  only  necessary  to  divide  or  break  across 
the  centre  of  the  part  drawn  out,  and  to  heat  the  surfaces  in  the 
flame  until  they  soften  and  become  round.  The  proper  mode  of 
severing  glass  rods  or  tubes,  is  first  to  make  a  deep  scratch  with 
a  three-cornered  file  in  the  spot  where  separation  is  required,  and 
then,  after  grasping  them  as  shown  in  Fig.  519,  by  gently  break- 
ing them  apart. 


608  TUBES   CLOSED — DRAWING   OUT  AND   CLOSING. 

Fig.  519.  The  tube  must  not  be  kept  in  the 

fire  too  long,  nor  yet  drawn  out 
too  rapidly.  When  the  tube  or  rod 
is  too  short  to  be  divided,  it  may  be 
drawn  out  at  either  of  its  ends  by 

means  of  a  punto — a  piece  of  glass  rod  which  is  heated  to  soft- 
ness and  cemented  to  the  other  as  a  handle. 

Tubes  Closed. — Very  small  tubes  may  readily  be  closed  by 

softening  their  edges  over  a  flame,  and  rotating  them  until  they 

unite  and  adhere.     Tubes  of  larger  size  are  treated  in  the  same 

way,  but  to  facilitate  their  closure,  occasional  pressure  of  the  hot 

end  against  the  back  of  the  tool,  Fig.  509,  and  sometimes  gentle 

blowing  through  the  open  end,  are  required. 

Fig.  520.  Tubes  also  are  closed  hermetically  by  draw- 

R  ing  out  one  end,  as  shown  in  Fig.  520,  by 

€i&feM     ^>=<r~ll    then  scratching  with  a  file  and    breaking 

asunder  the  part  #,  and  finally  by  closing 

the  small  orifice  by  fusion  in  the  flame. 

Drawing  Out  and  Closing. — When  it  is  desired  to  form  a  ves- 
sel like  a  test-tube,  a  tube  of  the  required  diameter  is  drawn  out, 
as  at  Fig.  521,  and  then  cut  asunder  at  a.  The  two  pieces  thus 
formed,  serve  to  make  two  test-tubes.  For  that  purpose,  it  is 
necessary  to  heat  the  smaller  end  of  each  to  softness,  and  imme- 


Fig.521. 


I 


Fig.  522. 


diately  upon  removal  from  the  flame,  to  blow  cautiously  and 
slowly  into  the  open  extremity  until  the  closed  end  assumes  a 
uniform  spherical  shape.  Sometimes  it  is  necessary  to  repeat  the 
heating  and  blowing,  in  order  to  fashion  the  bottom  perfectly,  as 
seen  in  Fig.  523.  If  the  piece  of  glass  is  only  long  enough  to 
form  one  tube,  its  end  can  be  drawn  out  by  attaching  a  punto,  as 
before  described,  and  now  shown  at  5,  Fig.  522.  This  punto,  or 


LATERAL  ATTACHMENTS.  609 

glass  rod  handle,  serves  also  to  remove  any  redun- 
dant glass,  it  being  only  necessary  for  that  purpose       Flg<  523' 
to  heat  the  closed  end  highly,  to  apply  the  punto  a 
little  less  heated,  and  after  collecting  upon  its  end  ,,,,TF-^ 

as  much  of  the  surplus  melted  glass  as  is  required  to 
make  the  bottom  thin  and  capable  of  supporting  sudden  changes 
of  temperature,  to  draw  it  off.  This  manipulation  requires  some 
dexterity,  which  is,  however,  easily  acquired  by  slight  practice. 
If  at  one  heating  and  gathering,  the  bottom  has  been  reduced  to 
the  proper  thinness,  it  may  be  heated  anew,  removed  from  the 
fire,  and  then  by  slow  and  gentle  blowing,  through  the  open  end, 
the  bottom  may  be  blown  out  to  roundness.  The  mouth  of  the 
tube  is  then  finished  as  directed  at  page  605,  Fig.  512. 

Lateral  Attachments. — To  attach  a  tube  to  the  side  of  another 
is  somewhat  difficult.  For  this  purpose,  the  tube  with  which  the 
junction  is  to  be  effected  is  closed  at  one  end  and  heated  at  the 
desired  point,  such  as  5,  Fig.  524,  to  high  redness.  To  this  hot 
part  a  glass  rod,  or  punto  c,  slightly  heated,  is  attached  and 
drawn  out,  as  shown  in  the  figure.  When  the  glass  has  cooled, 

Fig.  524.  Fig.  525. 


cut  off  the  new  joint  at  5,  heat  again  in  the  flame,  and  widen  its 
mouth  with  the  tool,  Fig.  507,  to  the  size  of  the  diameter  of  the 
tube  which  is  to  be  joined  with  it.  This  having  been  done,  the 
tube  is  to  be  attached  as  directed  at  page  606.  Fig.  525  shows 
the  joint  perfected. 

Another  mode  is.  to  heat  and  close  the  drawn  out  end,  and  to 
blow  forcibly  through  the  tube  until  the  bulb,  thus  formed,  bursts. 
All  the  remains  of  the  thin  glass  bulb  being  broken  off,  a  pro- 
truding aperture  is  left,  to  which  the  lateral  tube  may  be  ce- 
mented, in  the  usual  way,  by  heating  the  edges  of  the  ends  of  the 
two  tubes  to  be  united,  joining  them  in  the  flame  with  slight 
compression,  heating  the  joint  to  redness,  and  then  slightly  blow- 
ing, to  give  form  and  prevent  cracking. 

To  Blow  Bulbs. — To  form  a  bulb  at  the  end  of  a  narrow  tube, 

39 


610 


BULBS. 


Fig.  526. 


it  is  only  necessary  to  continue  heating  it  after  closure  until  it 
commences  to  soften,  and  then,  immediately  upon  its  removal 
from  the  flame,  to  blow  into  the  open  end,  as  in  Fig.  526,  slowly, 
until  the  heated  part  expands  to  the  proper  size  and  shape.  Care 
must  be  taken  to  heat  the  tube  to  a  suffi- 
cient extent,  so  that  there  may  be  enough 
glass  softened  to  give  a  bulb  of  the  re- 
quired size; — moreover,  during  both  the 
heating  and  blowing  the  tube  must  be 
kept  slowly  rotating  between  the  fingers, 
so  as  to  prevent  an  accumulation  of  the 
melted  glass,  by  its  own  weight,  in  any 
one  part. 

To  blow  a  bulb  in  the  middle  of  a  tube, 
the  latter  must  be  heated  at  its  centre 

during  constant  but  slow  rotation  between  the  fingers,  and  then 
carefully  blown  into  at  one  end,  whilst  the  other  is  closed  with 
the  finger,  a  cork,  or  a  piece  of  wax.  The  pressure  of  the  air 
within  expands  the  hot  glass  into  a  spheroid,  regular  or  irregular 
in  form,  according  to  the  care  and  skill  of  the  operator.  The 
part  of  the  tube  to  be  expanded  must  be  heated  uniformly,  and 
kept  in  constant  and  slow  revolution  during  both  the  heating  and 
blowing. 

In  the  fashioning  of  certain  glass-tube  apparatus,  it  is  some- 
times necessary  to  blow  the  bulbs  separately,  and  to  attach  them 
afterwards  to  their  adjacent  parts ; — the  bulb  is  then  formed  as 
follows.  Take  a  glass  tube  A,  Fig.  527,  of  the  required  dia- 

Fig.  527. 
i a 

u  ?  A. 


meter  and  length,  heat  it  at  the  points  a  and  5,  and  draw  it  out 
in  two  places,  as  shown  at  r  s  in  B.  When  the  tube  has  cooled, 
divide  it  at  the  attenuated  parts  r  8  with  the  file,  as  directed  at 
page  608,  Fig.  519,  and  close  one  end  of  one  of  the  pieces  in  the 
flame.  Then  hold  it  by  the  other  end,  which  is  drawn  out,  heat 


WELTER'S  TUBES. 


611 


it  to  redness,  and  fashion  the  bulb  by  blowing,  as  above  directed, 
until  it  assumes  the  shape  of  G.  It  is  then  cemented  to  the 
other  parts  of  the  apparatus,  as  directed  at  page  606,  the  pre- 
vious widening  of  the  drawn-out  parts  being  performed  as  at  Fig. 
512. 

Thermometer  bulbs  are  made  by  expanding,  as  above  directed, 
the  heated  end  of  tubes  with  a  capillary  bore. 

To  Make  a  Welter's  Tube. — By  way  of  illustrating  the  dif- 
ferent operations  of  fashioning  glass  tubes  over  the  blowpipe 
flame,  we  will  go  through  the  different  stages  of  manufacture  of 
the  safety-tubes  of  Welter.  A  straight  tube  is  first  bent  into 
form,  as  at  A,  Fig.  527,  and  the  flame  is  directed  upon  a;  as 

Fig.  528. 


ttt 


soon  as  the  glass  softens  at  that  point  one  end  of  the  tube  is 
closed  with  the  finger,  and  the  other  is  blown  into  forcibly,  so  as 
to  form  the  very  thin,  brittle  bulb  represented  by  the  dotted  lines. 
When  the  tube  is  thick,  a  repetition  of  the  heating  and  F.    52Q 
blowing  is  required.     This  bulb  is  then  broken  off,  and 
the  bent  tube,  thus  formed,  is  ready  to  be  attached  to 
the  straight  tube  B.     This  latter  is  formed  of  a  separate 
tube,  and  having  a  bulb  b  blown  into  its  centre,  is  ce- 
mented to  A  at  «,  in  the  manner  before  directed.     The 
funnel  top  of  the  tube  B,  is  formed  by  first  blowing  a 
bulb  c  on  its  upper  end  to  extreme  thinness,  removing  it 
with  the  file  and  cementing  a  bulb,  with  open  mouth,  as 
at  x  in  D.     The  s  form  is  given  merely  by  bending  B  in 
the  proper  direction. 


CORKS. 


"Instead  of  an  open  bull  at  the  top  of  the  D  tube,  a  small 
funnel  is  cemented  to  it,  as  in  the  fashioning  of  funnel-tubes, 
Fig.  529. 


CHAPTER  XXXI. 

CORKS. 

CORKS  are  in  many  ways  indispensable  for  laboratory  purposes, 
and  the  stock  should  consist  of  all  sizes ;  those  for  mounting 
apparatus  being  necessarily  of  the  finest  velvet  kind,  smooth  and 
as  free  as  possible  from  imperfections. 

An  excellent  means  of  increasing  the  elasticity  of  corks  is 
compression  by  a  small  apparatus,  Fig.  530,  sold  for  the  purpose. 

Fig.  530. 


This  treatment  renders  them  capable  of  being  fitted  to  apertures 
with  great  nicety  and  ease.  For  trimming  them,  as  may  be 
sometimes  necessary,  a  sharp  knife  must  be  used.  The  cut  sur- 
face can  then  be  made  perfectly  smooth  with  a  fine,  flat  file. 

We  have  frequently  made  mention  of  the  adaptation  of  tubes 
and  other  parts  of  apparatus  by  means  of  perforated  corks. 
These  perforations  may  be  made  with  a  hot  metallic  rod,  and 

Fig.  531. 


afterwards  enlarged  with  a  rat-tail  file;  but  a  much  smoother 
and  neater  hole  can  be  made  with  a  cork-borer,  Fig.  531,  which 


CORKS. 


613 


Fig.  532. 


is  intended  specially  for  this  purpose.  It  consists  of  a  series  of 
brass  tubes  of  uniform  length,  but  varying  from  an  eighth  to  one 
inch  in  diameter,  and  fitting  one  within 
the  other.  The  sizes  contained  in  such 
a  series  are  equal  to  all  the  requirements 
of  the  laboratory,  as  holes  of  smaller  or 
larger  dimensions  than  the  above  ex- 
tremes are  seldom  required.  Each  of 
the  tubes  is  open  below,  but  closed  at 
the  top  with  a  cap  c,  Fig.  532,  through 
which  is  a  hole  b  for  the  passage  of  a 
stiff  wire  d,  which  serves  both  as  a  handle 
and  as  a  punch  for  ejecting  the  cores 
from  the  tube  after  the  perforation  of 
the  cork. 

The  drawing  exhibits  one  of  the  tubes 
of  the  series  already  in  operation,  it 

being  only  necessary  to  bring  its  base  upon  a  cork,  and  to  effect 
the  perforation  by  pressure  upon  the  cap  and  a  slight  circular 
motion.  The  core  or  part  of  the  cork  removed,  ascends  into  the 
barrel  a  of  the  tube,  and  must  be  ejected  by  the  forcev  of  the 
punch  d.  As  the  tubes  become  dull  on  the  edges,  they  may  be 
sharpened  upon  a  grindstone  or  with  a  fine  file. 

As    a   familiar  illustration,  we  exhibit  in  Fig.    533  a  cork 
thus  treated,  with  tubes  inserted  in  the  perforations.     Their  con- 
Fig.  533. 


venience  is  shown  in  many  of  the  arrangements  of  which  we  have 
given  drawings. 

When  the  corks  are  not  of  good  quality,  they  may  be  rendered 
impermeable  by  coating  their  surfaces  with  soft  cement. 

India  rubber  corks  have  lately  appeared  in  the  market : — they 
are  made  by  Goodyear,  and  answer  admirably  as  cheap  stoppers 
of  bottles  containing  substances  which  are  volatile,  and  which 
do  not  corrode  the  caoutchouc. 


614  WEIGHTS  AND   MEASURES. 

CHAPTER  XXXII. 

WEIGHTS  AND   MEASURES. 

•  THE  following  tables  of  the  corresponding  values  of  French 
and  English  weights  and  measures  will  be  found  very  useful  for 
reference,  as  the  decimal  system  of  the  French,  owing  to  its 
greater  convenience  for  calculations,  is  extensively  adopted  in 
chemical  works. 

The  unit  of  the  French  weight  is  the  gramme,  which  is  the 
weight  of  the  hundredth  part  of  a  cubic  metre  of  distilled  water, 
at  the  temperature  of  melting  ice.  Below  are  some  comparative 
tables,  which  will  serve  to  give  every  explanation. 

Grammes.  Troy  Grains. 

Milligramme                  =                 -001  =  -01543 

Centigramme                 =                 -01  =  -15434 

Decigramme                   =                 •!  =  1'5434 

TROY  WEIGHT. 
English  weights.  French  weights. 

1  grain  =  ^  dwt.  =    0-06477      gramme. 

1  pennyweight     =  ^th  of  an  ounce  =     1-55456      gramme. 

1  ounce  =  ^th  of  a  Ib.  Troy  =  31*09130      grammes. 

1  pound  imperial  =    0*3730956  kilogramme. 

AVOIRDUPOIS   WEIGHT. 

English.  French. 

1  drachm                    =  y^th  of  an  ounce  =  1-7712         gramme. 

1  ounce                        =  y^th  of  a  pound  =  28-3384         grammes. 

1  pound  or  1  pound  imperial  =  0-4534148  kilogramme. 

1  cwt.         .                 =112  pounds  =  50-7824600  kilogrammes. 

1  ton                            =  20  cwt.  =  1015-6490000  kilogrammes. 


Grammes. 

Troy  grains. 

Gramme 

=3 

1 

— 

15-434 

Decigramme 

mm 

10 

= 

154-34 

Hectogramme 

= 

100 

== 

1543-4 

Kilogramme 

mm 

1000 

= 

15434 

Myriagramme 

= 

10000 

= 

154340 

Or: 

French.  English. 

1  gramme  =  15-438  grains  troy  =  0-643  dwts.  =  0-03216  oz.  Troy. 
1  kilogramme  =  2*68027  Ibs.  =  2  Ibs.  8  oz.  3  dwts.  6  grs.  Troy  wt. 
1  kilogramme  =  2-20548  Ibs.  =  2  Ibs.  3  oz.  4|  drs.  Avoirdupois. 
1  myriagramme  =  22 '0485  Ibs.  Avoirdupois. 
1  quintal  =  1  cwt.  3  qrs.  25  Ibs. 


WEIGHTS  AND   MEASURES. 


615 


The  unit  of  superficial  measure  is  "the  are,  a  surface  of  ten 
metres  each  way,  or  100  square  metres.  The  unit  of  measures 
of  capacity  is  the  litre,  a  vessel  containing  the  cube  of  a  tenth 
part  of  the  metre,  and  equivalent. to  0-220097  parts  of  the  British 
imperial  gallon.  The  standard  temperature  is  32°  F.  All  the 
divisions  and  multiples  of  the  units  are  decimal." 


MEASURES    OF    LENGTH. 


Myriametre 
Kilometre 
Hectometre 
Metre 


10,000  metres. 
1000       " 
100       " 
1       " 


Decimetre  — 
Centimetre  = 
Millimetre  = 


0-1  metres. 
0-01     « 
0-001  " 


MEASURES    OF  SURFACE. 

Hectare  =  1000  sq.  metres. 

Are  =  100         " 

Centiare  =  1         " 


Kilolitre 

Hectolitre 

Decalitre 


MEASURES   OF   CAPACITY. 


1000  litres. 

100     " 

10     " 


Litre 

Decilitre 

Centilitre 


1  litre. 

0-1 

0-01 


The  unit  of  solid  measure  is  the  stere,  or  cube  of  the  mStre, 
equal  to  85-31658  English  cubic  feet. 


MEASURES    OF   LENGTH. 
English. 

1  inch  or  ^  of  a  yard       ... 
1  foot  equal  =  £  of  a  yard  =  12  inches 
1  yard  =  3  feet         .... 
1  fathom  =  2  yards  ... 

1  pole  or  perch  =  5J  yards 
]  furlong  =  220  yards      - 
1  mile,  or  1760  yards         -         -         •    * 


LONG   MEASURE. 

French. 

=,         2-539954      centimetres. 
a         3-0479449    decimetres. 
=         0-91438348  metre. 
=         1-82876696      " 
=         5-  02  9 1 1 000  metres. 
=     201-16437000      « 
=   1609-31490000     « 


French. 
1  millimetre 
1  centimetre 
1  decimetre 
1  metre 
1  decametre 
1  hectometre 
1  kilometre 
1  myriametre 


0-039370 
0-393708 
3-937079 
39-37079 
393-7079 
3937-079 
39370-79 
393707-9 


English. 


=       1-093633  yards. 

=      10-936630      " 

=  109-366300      " 

=  4  furlongs,  213-633  yards. 

=*  6  miles,  1  furlong,  156-288  yards. 


616  WEIGHTS  AND   MEASURES. 

French.  English. 

1  toise  =  6-3945  feet  =  2-1315  yards  =  76-735  inches. 
1  aune  or  ell  =  3'893  feet  =  46'79  English  inches, 

SQUARE   MEASURE. 

English.  French. 

1  square  yard       -        -        -        -         -        -  =    0-836097  metre  carre*. 

1  rod  or  pole  =  30£  sq.  yards      •         •        -  =  25-291939  metres  carr^a. 

1  rood  =  1210  sq.  yards      -        -        -""•'   •  =  10-116775  ares. 

1  acre  =  4840  sq.  yards  =  40-4671  ares  =  0-404671  hectare. 

1  metre  carre"  =  1  centiare,  =  1*196033  sq.  yard. 

1  are  =  3-95  English  poles        .  V       -         -  =  0-98845    rood. 

1  hectare  =  2  acres,  1  rood,  5  perches,         -  =  2-473614  acres. 

MEASURES   FOR   LIQUIDS. 
English.  French. 

1  pint  or  fth  of  a  gallon  =  0-567932    litre. 

1  quart  or  ^th  of  a  gallon         =  1-135864    litres. 

1  imperial  gallon  =  4-5434579      " 

DRY   MEASURE. 

English.  French. 

1  peck  =     2  gallons  =     9-0869159  litres. 

1  bushel          =     8     "  =  36-347664        " 

1  sack  ==     3  bushels  ==     1-09043      hectolitre. 

1  quarter        =     8     "  =    2-907813    hectolitres. 

1  chaldron      =   12  sacks     =  13-08516  " 

French.  English. 

1  litre  =  1-760773  pints  =  '8803865  qts.  =       -2200966  gallons. 

1  decilitre =     2-2009667       " 

1  hectolitre         -        -        T     ,«***.*«"    =22-0096670       " 

As  a  greater  convenience  for  common  purposes,  the  French 
denominations  were,  in  1812,  arranged  as  follows : 

1  toise  or  6  feet  =  2  metres  =  6-5618334  English  feet. 
1  foot  or  12  inches  =  £  metre  =  1-0936389  "  foot. 
1  inch  or  12  lines  -  -  =  1-0936389  "  inch. 
1  line  -  •  «,7  *'  =  0-0911365  "  « 

1  aune  or  ell  =1  |  mdtre  =     3  937  English  feet: — Or, 
1  aune       -        *  ^'V**    =  47-244       tl         inches. 

1  bushel  =  f  hectolitre  ==  762-85  cubic  inches. 

1  old  Paris  foot  =  T066  English  foot. 
1  old  Paris  inch  =  1-066  "  inch. 
1  old  line  =»  O'OSSS  "  « 

The  metre,  the  square  metre,  and  the  cubic  metre,  are  the 
radical  standards  of  the  three  measures ;  for  there  are  only  three, 


WEIGHTS   AND   MEASURES.  617 

as  solidity  and  capacity,  differently  named  and  used,  are  the  same 
in  reality.  From  these  radical  denominations,  namely,  the  metre 
of  the  lineal  measure,  the  are  of  the  superficial  measure,  the  litre 
of  measured  capacity,  and  the  stere  of  solid  or  cubic  admeasure- 
ment, the  larger  ones  are  procured  by  multiplying  by  ten,  and 
the  lower  ones  by  dividing  by  the  same.  Thus, 


ti  prefixed,  means  10         times. 
Hecto,      «  «       100  « 

Kilo,         "  "      '1000         " 

Myria,      "  «       10,000       " 

The  number  is  understood  to  multiply  the  surface  of  the  solid 
and  not  its  side  ;  thus,  one  decare.  is  ten  ares,  not  a  square  of  ten 
times  the  side  of  an  are,  and  so  of  the  others. 

The  denominations  below  the  radical  ones  are  expressed  by  a 
sort  of  Latin  prefix  :  thus, 

.    Deci  is  one-tenth. 
Centi  is  one-hundredth. 
Milli  is  one-thousandth. 


INDEX. 


A 

ACIDS,  filtration  of,                 .•*  ••'*•   •• 

511 
328 
402 
116 

.    270 

oil,     

.    270 

liquid,  evaporation  by, 
desiccation  by,  . 
filter,         .... 

.    467 
.     479 
.    479 

Adie's  sympiesometer,    .        .  •>  •'  .. 
Adjustment  of  balances,  . 

Balloons  for  weighing  gases,  . 
Barometer                         . 

.     126 
.    386 

Air,  analyses  of, 
heated,  evaporation  by,    . 
Air-pump,        ....       70 

546 
468 
126 
225 
231 

135 

396 
200 
522 
549 
582 
403 
547 

.    386 

Wheel  

.    387 
.     389 

.    388 

.     389 

Alexander's  method  for  taking  speci- 
fic gravity,     .... 

Troughton's,     . 
Hassler's, 
Alexander's, 

.    391 
.     394 
.    396 
.    399 

Alkalimeter,  Schuster's, 
Amalgam  for  electrical  machines,  . 
Amalgamating  battery  zincs,  . 
Analysis  by  blowpipe,     . 
Aneroid  barometer, 
Anode,     

Morland's  diagonal,  . 
Adie's  sympiesometer, 
Aneroid,  .... 

.     400 
.     402 
.    403 
.    406 

Water,      . 
Wollaston's,     . 
Regnault's, 

.    402 
.    407 
.     407 
.    407 

Areometer,                        '. 

134 

134 
,  69 
345 
312 
113 
225 
537 

28 
101 
102 
108 
111 
113 
113 
114 
115 
116 
533 
131 
271 
%*> 

Argand  burner,        ...        64 
Arsenic  apparatus,  Marsh's,  . 

construction  of,         .    ",..*# 
adjustment  of,   . 

.     408 
.    410 
.     411 

Assay  balance,        .... 
furnace,     ..... 
Astatic  galvanometer,    . 

B. 

Barren's  furnace,     .        .        . 
Barometric  corrections,   . 
Batteries,  electrical,        .       ^-^ 

.     226 
.    414 
.    525 
.     547 

efficiency  of, 
construction  of,  . 
local  action  in,    . 
amalgamating,   . 
Wollaston's, 
Daniell's,    . 
Smee's, 
Grove's,     . 
Bunsen's,  . 
connections, 
wire  for,     . 
arrangement  of, 
power  of,    . 
for  plating,  . 
Baume's  hydrometer, 
tables  for,  .        .        . 
Beale's  gas  furnace, 
3eindorfl  's  apparatus, 
Bennett's  electrometer,  . 

.    549 
.     549 
.    549 
.     549 
.     549 
.     551 
.     553 
.     554 
.     555 
.     556 
.     557 
.    562 
.     562 
.     566 
.     145 
.     145 
.     246 
.      54 
.    530 

description,  test,  and  use  of,     . 

Kater's  and  Robinson's,  . 
Berlin,       . 

Assay,       
Tralle's  

Platform,  . 
preservation  of, 
adjustment  of,  . 
Torsion,  Coulomb's                 •» 
Hydrostatic, 
Baths,  sand,     .        .                 31,  66, 

266 
268 

saline,       .        .        .                +' 

620 


INDEX. 


Bell  glasses 368 

for  weighing  gases,   .        .        .     126 

Berlin  balance,      '  .        .        .        .     Ill 

Berzelius'  lamp,       .        .        .        .233 

combustion  tube,      .        .  307 

washing  bottle,          .        .        .    415 

Binding  screws 556 

Black  lead  crucibles,       .        .        .279 

flux, 294 

Bladder, 381 

Blast  furnaces,          .        .        .        .219 

lamp,  Deville's,         .        .        .238 

Nunn's,      .        .        .        .239 

Sonnenschein's,         .        .    257 

B lowing  glass,    '•'.        .        .      69,601 

Blowpipe  table,        ....      69 

compound,         .        .        .        .251 

mouth, 572 

Gahn's,  .  .  .  .  .574 
Mitscherlich's, .  •  .  .575 

De  Luca's 575 

gas-lamp,  .  576 

lamp,  Harkort's,  576 

use  of,        .        .  577 

the  flame,  .        .  578 

oxidation,  .  580 

reduction,          .-.  58i 

supports, 582 

instruments  for  analysis,  .  .  585 
Herapath's  tables  for  testing  by, 

.    596-600 

reagents,  ....  590,  593 
table,  .  .  .69,  594,  603 
testing  by,  ....  595 

Blue  pots, 279 

Boiling, 445 

by  steam, 450 

in  beaker  glasses,  .  .  .  448 
tubes,'  .  .  „  .445 
flasks,  .  .  .  .448 
capsules,  .  .  . .  .  449 

Bottles, 73 

labels  for,          76 

for  test  series,   .        ...       83 
Bottles  for  spec,  grav.,    .        .        .     132 

Wolffe's 351 

Spritz, 506 

Washing,  .        .        .        .        .507 

Berzelius's,        .        .        .    515 

Gmelin's,  ....    516 

Cooke's,     .        4        .        .517 

Bronze  Powder,       .        .        .        .569 

Bronzing, 572 

Bunsen's  Battery,    ....    555 
Bulbs,  glass,  blown,        .        .     609,610 


C. 


Cadet's  apparatus,  ....  458 
Calcination,  .  .  .  .  298 

Calcining  furnace,  ....  223 
Calorific  electrometer,  .  .  .  533 
Calorimotor,  Hare's,  •  .  .  .  564 
Capsules,  ....  450,  463 

Caoutchouc, 380 

for  joints,  .  .        .        .381 


Celsius  thermometer,      .        .        .  208 

Cement,  soft, 382 

resin, 382 

iron,  ......  383 

for  glass,    .        .        .        .        .383 

steam  joints,       .        .        .  384 

labels 385 

Centigrade  thermometer,         .  208 

Charcoal  for  fuel,     ...  228 

Chemical  tables,      ...  191 

reaction,  crystallization  by  477 

Chloride  of  calcium  tube,         .  489 

Cistern  barometer,  .        .        .  388 

Clarke's  combustion  tube,       .  307 

Cleaning  of  glassware,     .        .  77 

Cloth  filters,     ....  509 

Coffee's  syphon,       .        .    v.  496 

Cohobation,      .        .        .        «  '  340 

Collection  of  gases,  .        .        .  350 

over  air,     .....  372 

Combustion  in  glass  tubqs,      .        .  308 

Condensers, 324 

Gedda's, 48 

Schrader's 324 

Liebig's 330 

Compound  blowpipe,        .        .  251 

Ritchie's,           ...  255 

Tale's,       ....  256 

Cooke's  washing  bottle,          .  517 

Copper  solutions  for  electro-metal 

lurgy,     ....  570 

Cooling  mixtures,    .        .        .  272 

table  of, 274 

Corks 612 

fitting  of,  .        .        .        .    612,  613 

borer,         .        .        .                 .  613 

612 

Coulomb's  electrometer, 
Crown  of  cups,         ..       , 
Crucible  jackets, 
Crucibles,  clay, 

black-lead,  •  -.'-« 
porcelain,  .  .  i 
iron, 


533 
547 
234 
278 
279 
279 
281 

silver, 281 

platina,      .....    282 

use  of, 284 

Crushing, 88 

Crystals,  purification  of, .         .        .    475 

drying  of, 479 

Crystallization,         ....    472 

by  fusion, 472 

sublimation,         .        .        .    472 
Crystallization,  by  solution,   .        .    473 

granular, 474 

by  chemical  reaction,        .        .    477 
Cupel,  furnace,        ....     225 

Cupels, 310 

Cupellation 312 

Curtains,  with  spring  rollers, .  .  22 
Cushions,  for  electrical  machines,  .  522 
Cylinder,  "  "  "  .  519 


D. 

Daniell's  pyrometer, 
battery,     . 


205 
551 


INDEX. 


621 


561 
301 
575 
129 

478 
479 
479 
480 
485 


Darcet's  digester,    ....    442 
Decantation,    .....    493 

washing  by,      .        .        .        .    494 

Decoction, 438 

Decolorization,        •„',      «        .        .511 
Deflagration,    .        .        .        .        .300 

by  electrical  action, . 
Decrepitation, 
De  Luca's  blowpipe, 
Densities  of  bodies, 
Desiccation  of  solids, 
of  filters, 

by  water-bath,          »,^ 
hot  air, 

of  easily  alterable  substances, 

in  vacuo,    .....    487 

of  liquids,          .        .'       .        .488 

gases,          .        .        .        .488 

apparatus  for,      .        .     489 

Deville's  blast  lamp,       .        .        .238 

gasometert        ....     365 

Diaphragms,  for  batteries,       .        .    553 

Differential  thermometer,       .         .211 

galvanometer,  .  .      ..V    .        .    539 

Digestion,         .       /«.  .'    *<      «.       .    439 

in  beakers,        .  .        .    440 

flasks 441 

under  pressure,         .        .        .     441 

Digesters,  Papin's, ....    441 

D'Arcet's,         .        .        .        .442 

Mohr's,     ,        .        .        .        .    444 

Displacement, 452 

solution  by,        ....    452 

Robiquet's  apparatus,      .        .     453 

Payen's,  "  .        .    455 

Distillation,  .  314,  334 

of  liquids,          .         .        .        .335 

gases,          .         .        .         .340 

in  tubes,  .        .        .        .        .330 

retorts,         .        .        .        .    325 

vacuo,          ....    374 

dry, 375 

micro-chemical,        .        .        .    330 

by  steam, 373 

destructive,       ....    375 

Discharger,  electrical,     .        .        .    527 
Dippers,  .        .        ....        .        .     507 

Donovan's  filtering  apparatus,        .    512 
Dropping-tubes,       ....    201 

Drummond  light,     ....    254 

Drying-tubes, 489 

chamber,    ....      32 
Duvoir's  boiling  vats,      .        .        .46 


E. 


Earthenware  retorts,  .  .  .333 
Ebullition,  .  ',  .  »  . .  .  .  445 
Edulcoration,  ....  515 

Efflorescence,  .        .        .        .478 

Electrical  machine,  cylinder,          .     519 

plate, 521 

construction  of,  ...  522 
cushions  for,  ....  52$ 
amalgam  for,  ....  522 
conductors  for,  .  .  .  222 
preparation  for  use  of,  .  .  523 


Electrical  battery,    ....  525 

discharger,        ....  527 

relations  of  the  metals,     .        .  548 

conducting  power  of  the  metals,  549 

decompositions,         .        .        .  558 

currents,    .....  558 

Electricity, 519 

detection  of,               .        .  529 

measurement  of,                        .  529 

applications  of,          .        .        .  542 

from  galvanic  action,        .        .  547 

Electro-magnetic  multiplier,           .  536 

Electrometer,  Henly's,    .        .        .  529 

Bennett's,       '  ;    .'.:...        .  530 

Coulomb's,        .    '•••.-'    "f        .  533 

Lane's,      .        .        .        .        .  534 

Calorific,            ....  534 

Electrodes, 558 

Electrolytes, 558 

Electrolysis,     .....  558 

Electrotype,     .        ..      .    -  .-.,        .  567 

Electro-metallurgy,          .        .        .  566 

copying  by,        ....  567 

plating  by,        ....  567 

moulds  for,       ....  567 

non-conducting  substances,       .  568 

solutions,           ....  569 

arrangement  of  batteries  for,    .  571 

Electroscopes,          ....  529 

voltaic  pile,        ....  532 

Electrophorus,          ....  527 

Etching  on  glass,     ....  79 

Eudiometer, 542 

use  of, 543 

Ure's,         .         .        .        .        .'545 

Hare's  aqueous,         .        .        .  563 

Evaporating  vessels,        „        .        .  463 

Evaporation,     .....  463 

spontaneous,      .  464 

in  vacuo, 465 

by  heat  in  open  air,  .         .        .  467 

liquid  baths,        .        .        .  467 

steam,        ....  467 

heated  air,          .        .        .  468 

over  sandbath,           .        .        .  468 
naked  fire,          .        .        .471 


F. 


Fahrenheit's  thermometer,     .        .    208 
Faraday's  table  for  estimating  the 
amount  of  watery  vapor  in 

gases, 127 

voltameter,        ....    560 

decomposition  tube,          .        .    561 

Filter  stands,  ....    262 

bath,  .        „       ».       .        .    479 

Riouffe'a,  .        .        .        .512 

Filters  ignition  of,    «        •        .        .    287 

drying  of,  ....    479 

paper, 498 

cutting  of,  .        .        .        .    499 

folding  of,  .        .        .        .502 

cloth,         .        .        .        .     •  .    509 

frames  for.         .       '.        .        .510 

washing  of,        ....    513 

Filtering  paper,  German,        .       »    498 


622 


INDEX. 


Filtering  paper,  Swedish,        . 

.    499 

purification  of,    •        . 

.    499 

light,         . 

.     561 

497,  505 

battery,  Smee's,       .        . 

.     553 

through  paper   .        .        , 
of  oils  and  viscous  liquids, 
through  cloths,          .      «. 
pulverulent  matter,    . 

.     498 
.     508 
.    509 
.     511 

Daniell's,   .  -      •      ,^i 
Grove's,     . 
Bunsen's,           y,    ?& 

.     551 
.     554 
.     555 
.     547 

.    508 

decomposition  by,     .        . 

.     558 

.of  corrosive  liquids,  . 
volatile         " 
Fire  lute,          .... 
Flame    ftlowpipe,    ... 

.    511 

.     512 
.    383 

.     578 

reduction  by,    . 
Galvanometer, 
Schweigger's,  .        .        . 

.    561 
.     535 
.     536 
.     537 

Flasks,  Florence,    . 
sublimation  in, 

.     346 
.     317 

.    448 

differential, 
Weygandt's,     . 
Gas  chamber,          ... 

.     539 
.     539 
55 

.     381 

64,  240 

.     303 

apparatus   Kent's,    .        . 

.     241 

Florence  flasks, 
Florentine  receivers,        •*     f<& 

.     346 
.     339 

manufacture  of, 

.     242 

.    242 

Fluids,  measuring  of,       .     -«f  i 
spec  grav  of,    .        .        . 

.     194 
.     139 

grease, 

.     241 

66 

Flux,  black,      .... 
Fluxes,  ignition  with,      •        . 
non-metallic,    ... 

.     294 
.     290 
.     291 

Beale's,      . 
Hoffman's, 

.     246 
.    247 
.     250 

.     297 

hydrogen  apparatus,         • 

.     348 

Freezing  mixtures, 
tables  of, 
French  crucibles, 
Fuel  for  furnaces              .        . 

.     271 

.     274 
.     279 
.     228 

jars,  
regulator,  Kemp's,  . 
burner  for  blowpipe, 

.     368 

.    481 
.    576 
304,  360 

Funnels,  filtering, 

.    498 
500 

collected  over  water, 

.    365 
.     372 

porcelain, 

.     501 
.     501 

mercury,    . 
receivers,          .        .        . 

.    369 

.     350 

stands  for,                  «•       • 
Furnace-room,         .        ••      V 

.     504 
.      29 
.    229 

illuminating,     . 
distillation  of,    . 
Gases,  weighing  of,         .        • 

.     240 
.     340 
.     126 

.     223 

spec.  grav.  oft  ... 

.     147 

.     225 

measurement  of,       .        • 

.     202 

30,  218 

collection  of,     •        .        . 

.     350 

.     219 

generation  of,  •        .        * 

.     354 

.     220 

absorption  of,    ... 

.     356 

universal, 

.     221 
.     222 

transfer  of,        ... 

.    372 
.    424 

reverberatory,  . 

.    223 

.    225 

desiccation  of,  . 
Gasometers,    .... 

.    488 
.     360 

Aiken's 

.     225 

Peov's 

.     361 

assay  or  cupel,  . 

.     225 
226 

mercurial, 
D^ville's, 

.     363 
.    365 

.     227 

Gay  Lussac's  barometer, 

.     399 

furniture  for, 
gas,            .... 

.     228 
'66,  246 
.     568 

Generator,  steam,    . 
German  filtering  paper,          . 
Glassware,  cleansing  of,         . 

.      35 
.     498 
.       77 

Fusing-points           ... 

.    286 

.     326 

Fusion                               -.        . 

277  285 

.    499 

crystallization  by, 
by  electrical  action, 

.    472 
.     562 

cement  for,               .   "    # 
etching  upon, 

.    383 
.      79 
69,  601 

.     277 

•    implements  for         .        . 

.     604 

G. 

Gahn's  blowpipe,    . 

.     574 
.     252 

tubes,        .                 .        . 
blower's  lamp, 
bulbs,  blown, 
cutting  of, 
tubes,  bent, 
cemented,          .        . 

.    307 
.     601 
609,  610 
.     601 
.    606 
.    606 

Galvanic  action,      .        .        . 

.    547 

.     608 

batteries, 
arrangement  of, 
power  of,  . 

.     548 
.     562 
.    562 

divided, 
drawn  out, 
Glass  tubes,  edges  of,  rounded, 

605,  608 
.    607 
.     605 

INDEX. 


623 


Gmelin's  washing-bottle,       .        .  516 

Gold  solutions  for  electro-gilding,  .  569 
Goodall's  grinding  and  levigating 

apparatus, 94 

Graduation  of  vessels,    .        .        .  194 

Granulation,    .....  474 

Gravimeter, 141 

Grove's  battery,       ....  554 

Gutta  percha,  for  moulds,       .        .  568 


H. 


Hare's  compound  blowpipe, 

eudiometer, 

calorimeter,       .        .  .;  . 
Harkort's  blowpipe  lamp, 
Harris's  machine  sieve,  . 
Hart's  gas  furnace, 
Hassler's  barometer, 


.  251 
.  563 
.  564 
.  576 
.  97 
.  250 
.  394 

Heating  by  baths,    .        .        .        .264 

steam,       .....    265 

in  close  vessels,        .        .         .    377 

by  hot  air,         ....    468 

Heat  from  galvanism,      .        .        .    561 

Henley's  electrometer,    .        .        .    529 

Henry's  subliming  apparatus,          .    320 

Hessian  crucibles,  .        .         .    278 

Herapath's  tables  for  testing  by  blow- 

pipe, 596-600 

Hewitt's  machine  mortar,        .        .       93 

Hoffman's  gas  furnace,    .        .        .    247 

Hoods  for  carrying  off  noxious  vapors,    34 

for  retorts,         .        .        .        .334 

Hydrogen,  reduction  by,         .        .    302 

gas  apparatus,      ....    348 

Hydrometers,  «.       .        .        .     140 

Baume's 14 

Hydrostatic  balance,        .        .        .131 
Hydro-sublimation,      .    .        .        .320 


Igneous  fusion,        •        •        .        .27 
Ignition  with  fluxes,        .        .        .    290 
of  filters,    .        .        .        .        .287 
in  vapors,      ;    •        •'      .  290 

604 
299 
84 
304 
303 
304 


Implements  for  glass-blowing, 
Incineration,    .... 
Index  rerum,   . 
India  rubber  connecting  tubes, 

for  joints,  .... 

gas  bags, 


Infusion, 437 

Ink  for  labels, 80 

Iron  crucibles,          .        .        .        .281 

tubes, 309 

retorts,      •,    '  ,.      .        .        .33 

cement, 382 

Jacket  for  crucibles,        .        .        .    234 

Jars,  gas, 368 

Leyden,   »       «.       ,        .        .523 


K. 


Kater's  balance,     .       .       .       .108 


Kathode,  . 

Kemp's  generating  jar, 

gas  regulator,    . 
Kent's  furnace, 

gas  apparatus,  . 


Labelling  of  bottles, 
Labels  etched, 

paste  for,  .... 

ink  for,      .... 

varnish  for, 
Laboratory,  arrangement  of,   . 

heating  of, 

ventilation, 

plan  of,  .        •        . 

materials  for,    . 

jack 

water  for,          . 

cleansing  apparatus, 

costume,  . 

record,      .        .        .      •••£•>•"• 
Lamp,  alcohol, 

Danger's, 

glassblower's,  . 

oil,     .        .        . 

pyroxylic  spirit, 

Berzelius's, 

supports, 

Luhme's, 

Rose's,      .... 

Russian,    .... 

Deville's  blast, 

Nunn's      "      .        « 

table  gas,  .... 

tongs,        .        .        .      •:.»  # 

heating  oven,     . 
Lane's  electrometer, 
Leslie's  differential  thermometer 
LetorelPs  gas  receiver,    . 
Levigation,      .... 

by  machinery,  .        ,       .4^1* 

by  decantation,  .  • 
Leyden  jars,  .... 
Liebig's  furnace,  .  . 

combustion-tube,      .      :»...••/ 

drying-tube,      .        .      -4.*;* 
Lime  cement,  .... 
Liquids,  weighing  of, 

measurement  of, 

distillation  of  volatile, 

distillation  of,   . 

solution  of, 

evaporation  of,  . 

desiccation  of,   .        .        . 

filtration  of  corrosive, 
volatile, 

electrical  decomposition  of, 
Lutes 

mode  of  applying,     . 

lime,         .... 

plastic,      .... 

resinous,   . 

iron, v 

fire,   .        . 

Local  action  in  batteries, 
London  crucibles,    . 


64 


548 
347 
481 
222 
241 


.  76 

79 

80 

80 

80 

17 

19 

19 

21 

21 

36 

56 

58 

84 

84 

231 

601 

601 

231 

231 

233 

235 

236 

237 

237 

238 

239 

240 

232 

230 

534 

211 

356 

98 

94 

494 

523 

227 

307 

489 

382 

124 

194 

329 

335 

423 

463 

488 

511 

512 

558 

380 

385 

382 

382 

382 

383 

383 

549 

278 


624 


INDEX. 


M. 

Maceration,     .  .        . 

Machine  for  slicing,         . 

crushing,  .  .  .  . 
Magnets,  .... 
Marsh's  arsenic  apparatus,  . 
Measures  and  measuring, 

and  weights,  tables  of,     . 

equivalent  weights  of, 
Measurement  of  fluids,   . 

gases,        .... 

temperature,     .        .        . 

electricity,         .        . 
Melloni's  thermo-multiplicator, 
Mercurial  gasometer, 
Mercury  trough,      .        .        . 

bath,  .... 
Metallic  baths, 

fluxes,        .        . 

tubes,        .... 

retorts,      .... 

crucibles, 
Metals,  pulverization  of, 

electrical  relation  of, 

conducting  power  of, 
Micro-chemical  distillation,     . 
Mineral  cases,          %       .        . 
Minimeter,  Alsop's,         .    .=-.••> 
Mint  balance,  .        .        . 

Mitscherlich's  blowpipe, 
Mixtures,  freezing,         •>•..}**! 
Mohr's  dropping-tube,     .        . 

digester,  .... 
Morland's  barometer,  .  . 
Mortars,  •  .,. 

iron,        '  ?,    •  +       . 

steel,         V      . 

agate 

porcelain,  . 

Wedgwood, 

glass,  .... 
Muffles, 

Taylor's,    *  v»  .  &» 


.  437 

.  87 

.  88 

.  589 

.  345 

.  194 
614,  617 

.  199 

.  194 

.  202 

.  205 

.  529 

.  211 

.  363 

.  369 

.  270 

.  270 

.  297 

.  309 

.  331 

.  281 

.  91 

.  548 

.  549 

.  330 

.  25 

.  201 

.  102 

.  575 

.  271 

.  201 

.  444 

.  400 

.  89 

.  90 

.  91 

.  92 

.  93 

.  93 

.  89 

.  225 

.  313 


N. 


Newman's  barometer,     .        . 
Nicholson's  areometer,   .        . 
Nobili's  galvanometer,   .        . 
Nunn's  blast  lamp,          .        . 

0. 

.    389 
.     134 
.    537 
.    239 

.    241 

baths,        .    ,    . 
filtration  of,       ... 

.     270 
.    508 
.    576 

Office,  arrangement  of,    .  • 
furniture, 
Operating  table, 

.      25 
.      27 
61,  67 
61 

Ores,  pulverization  of, 
Organic  analysis, 
furnace  for,       .        .        , 

.      91 
.     226 
.    227 

Oxygen  apparatus,          .  .    252 

O  xy hydrogen  blowpipe, .        ..       .    251 


P. 


Paper  filtering,  *  •  .  .  498 
Paste  for  labels,  .  .  .  .80 
Papin's  digester,  ,  .  »  .441 
Pepy's  gasometer,  ...  361 

Pipettes,  ....     199,  495 

Plaster  of  Paris  lute,  .  ,'•  .  382 
Plastic  lute,  .  .  .  .  .382 
Platform  balance,  .  .  .  .114 
Platina  crucibles,  .  282 

retorts, 331 

Platinized  silver,  ....  553 
Pneumatic  pump,  ....  70 

trough, 365 

Poles  of  a  battery,  .  .  .  .547 
Porcelain  crucibles,  .  .  .  279 

tubes, 308 

retorts, 333 

funnels,     ...        .        .        .500 

Porphyrization,       .  .95 

Potash,  bulbs,         ...  .353 

Precipitation,  ...  .    491 

Precipitates,  desiccation  of,  .    479 

washing  of,  .     493 

Precipitating,  directions  for,  .    492 

vessels  for,        .        .  .    492 

by  galvanism,  .        .  .    570 

Pressure,  digestion  under,  .    441 

Pump,  air, 70 

Purification  of  crystals,  .  .  .  475 
Putnam's  curtain  spring  rollers,  .  22 

Pulverization, 89 

of  metals, 99 

Pyrometer,      .        .        .        ,        .205 


Q. 

Quantity  of  the  galvanic  fluid, 


R. 


551 


Reaction,  chemical,  crystallization 

by, 477 

Reagents, 80 

blowpipe,  .        .  .     590, 594 

Reaumur's  thermometer        .        .  208 

Receivers,        .        .  .    336, 327 

Florentine,       .                        .  339 

gas,  ...                          .  350 

Lettorel's, .                 .        .  356 

Record  of  analyses, .                .        .  84 

Rectification,    .        .                 ,  340 

Reduction  by  chemical  means,       .  99 

charcoal, 301 

hydrogen,          .        .        .        .  302 

apparatus,          .        .        .        .  303 

tubes, 306 

Register,  barometer,       .        .        .  407 

Regnault's       "                ...  407 
Resinous  lutes,        .        .        .        .382 

Retorts,  sublimation  in,  .       .       .  318 


INDEX. 


625 


Retorts,  distillation  in,    . 

glass,         . 

platma,      . 

earthenware,    . 

iron, 

porcelain, . 

lutes  for,   .... 
Reverberatory  furnace,  . 
RioufTe's  filtering  apparatus, 
Ritchie's  compound  blowpipe, 
Roasting,         . 

in  tubes,    .... 
Rose's  combustion  tube, 

lamp,         . 
Robinson's  balance, 
Rosin  gas,        .... 
Rubber  of  electrical  machine. 
Russia  lamp, 


S. 


Safety  tubes,  ..... 
Saline  baths,  ..... 
Salts,  solubility  of,  .  .  .  419, 

table  of,    ..... 
Sand  bath,       .        .'J'-     ,         31,  66, 

evaporation  by, 
Saturation,       ..... 

Schweigger's  galvanometer,    . 
Schuster's  alkalimeter,    . 
Sefstrom's  blast  furnace, 
Separating  funnels, 
Sieves,      .        ».      'v        • 
Sifting,     ...... 

Silver  crucibles,       „ 

solutions  for  electro-plating,     . 

platinized,          .        .        .        . 

Sink,  the,         ..... 

Slicing,     ...... 

Smee's  battery,       .... 

Solids,  weighing  of,          ... 

spec.  grav.  of,   .        .        .        . 

solution  of,         .... 

desiccation  of,  ... 

Solubility  of  salts,    . 
Solutions,  saturated,  boiling-point  of, 

decolorization  of,  .        . 

Solution,  ...... 

means  of  facilitating, 

of  solids,    ..... 
liquids,        ..... 


325 
326 
331 
333 
332 
333 
384 
223 
512 
255 
299 
307 
307 
237 
108 
242 
522 
237 


, 

by  digestion,      .. 

under  pressure, 

boiling,       .. 
in  test-tubes,     .. 

beakers,      .. 

flasks,          .. 

capsules,     .. 
by  steam,  .. 

displacement,     . 
in  volatile  solvents,  . 

close  vessels, 
Cadet's  mode  of,       . 
under  pressure  of  steam, 
Duvoir's  apparatus, 
crystallization  by,     . 


359 
268 
426 
426 
271 
468 
418 
536 
200 
225 
501 

97 

95 
281 
570 
553 

56 

86 
553 
122 
129 
421 
478 
426 
269 
511 
417 
420 
421 
423 
424 
439 
441 
445 
446 
447 
448 
449 
450 
452 
454 
457 
458 
461 
462 
473 

40 


Sonnenschein's  blast-lamp,     .        .    257 
Specific  gravity,       .        .        .        .129 

bottles, 132 

by  areometer,    .        .        .134,  143 
Alexander's  method,  .    135 

of  fluids 139 

by  the  flask,     .        .        .        .139 
hydrometers,      .        .     140,  144 

Sravimeter,        .        .        .     141 
am's  method,          .        .     146 

of  gases 147 

vapors,       .        .        .        .150 

tables  of, 154 

Spirit  lamps,  ,  232 


Spritz  bottles, 

Spontaneous  evaporation, 

Steam  generator, 
series, 

bath,          .        .        , 
distillation  by,  . 
joints,  cement  for,     . 
solution  by, 
evaporation  by, 

Stills, 


506 
.  464 
.  35 
.  43 
.  265 
.  373 
.  384 
450,  461 
.  467 
48,51,322 


furnaces  for 52 

Stock  for  laboratory,  ...  83 
Stoneware  retorts,  ....  333 
Sublimation,  ....  315,  472 

in  tubes 316 

flasks, 317 

retorts,  ;  .  .  .  .318 
shallow  vessels,  .  .  .319 
by  Henry's  process,  .  .  320 

lire's, 320 

Sulphur  moulds,  ....  568 
Supports  lor  lamps,  .  .235,  259 

retorts, 260 

universal, 260 

Gahn's, 261 

for  funnels,  ....  504 
Swedish  filtering  paper,  .  .  ,  499 
Sympiesometer,  Adie's,  ,  .  402 

Syphon, 495 

use  of 496 

Coffee's, 496 

barometer,  ....  389 
eudiometer,  .  546 


T. 


Table,  operating,  .  .  .  61,  67 
blowpipe, ..  .  .  69, 594, 602 
glass  blowers'  ....  69 
for  balance,  .  .  .  .115 

Table  furnace,         ....    220 

Tables,    Faraday's,  for    estimating 
watery  vapor  in  gases,         .  127 

.for  Baume's  hydrometer,         .      145 
of  spec,  grav.,  ...  154 

chemical,  ....  191 

Tables  of  measures,  .  .  199,  615 
freezing  mixtures,  .  .  274 
thermometrical  equivalents,  213 
solubility  of  salts,  .  .  426 
boiling-point  of  saturated  solu- 
tions,   269 

electrical  relations  of  the  metals,  548 


626 


INDEX. 


Tables  of  electrical  conducting  power 

of  metals,  .  .  .  .  549 
of  weights  and  measures,  614,617 
Herapath's,  for  testing  by 

blowpipe,       .        .        .    596,  600 

blowpipe,  ....    594,  602 

Tasker's  water  furnace,          .         .      19 

Temperature,  measurement  of,       .    205 

Test-tube  racks,      ....      58 

stands, 63 

case, 79 

series, 80 

bottles, 83 

papers,       .        .        .        .        .88 

tubes,  solution  in,     .        .        .    446 

Testing  by  blowpipe,       .        .      ..595 

Thermometers,        .        ,        .        .207 

Celsius, 208 

Fahrenheit,       .        .        .        .208 

Reaumur,  .        .        .        .209 

differential,        .        .        .        .211 

Thermometrical  equivalents,  .    213 

Thermometrograph,        .        .        .211 

Thermomultiplicator,      .        .        .211 

Thermostat,  Kemp's,      .        .        .481 

Tongs,  furnace,        .        .        .        .    229 

lamp, 232 

cupel, 312 

Tool  chest, 60 

Tralle's  balance,     .        .        .        .113 
Transfer  of  gases,    ....    372 

Trituration, 92 

Torsion  balance,  Coulomb's,  .        .    533 

Troughs,  pneumatic,       .        .        .    365 

water,        ....        .    366 

mercury, 369 

Troughton's  barometer,  .        .        .391 

Tubes,  porcelain 308 

metallic, 309 

combustion,      ....    307 

reduction, 307 

flexible,     .        .        .        .-       .    303 
graduation  of,    .        .        .        .197 

iron 309 

platina, 310 

safety, 359 

test, 446 

drying,      .        .        .     484,  489, 490 
chloride  of  calcium,  .        .        .    489 

U, 490 

Faraday's  decomposition,         .    560 
glass,  attachments  to,       .        .    619 

bent, 606 

cemented 606 

closed 608 

drawn  out, ....  607 
divided,  .  .  .  605,608 
edges  of,  rounded,  .  .  605 
.  funnel,  blown,  .  .  .  -611 
Welter's  blown,  .  .  611 


U. 


U  tube, 


490 


Universal  furnace,    .        .  .  .221 

Kent's,        .        .  .  .222 

Ure's  subliming  apparatus,  .  .    320 

eudiometer,       .  .  .    545 


V. 

Vacuo,  distillation  in, 

evaporation  in,  . 

desiccation  in,   . 
Vapors,  noxious, 

spec,  gravity  of, 

ignition  in, 
Varnish  for  labels,    . 
Ventilation  of  laboratory 
Vessels  exhausted  of  air, . 

graduated, 

Viscous  liquids,  filtration  of, 
Volatile  liquids,  distillation  of 
filtration  of, 

solvents,     . 
Voltaic  pile,      ..       .. 

electroscope,     . 


W. 


.  374 

.  465 

.  487 

.  34 

.  150 

.  290 

.  80 
19,  34 
70,  126 

.  194 

.  508 

.  339 

.  512 

.  454 

.  547 

.  532 


Washing  precipitates,  .  .  .  493 
by  decantation,  .  .  494,  513 

bottles 507,  513 

filters, 513 

Water-bath,  .....  266 
trough,  .  .  ,  .  .  366 
barometer,  ....  402 
decomposition  of,  .  .  559 

mother, 474 

gas  collected  over,  .  .  .  365 

Wedgwood's  pyrometer,         .        .    205 

Weighing, 120 


solids, 
liquids 


122 
124 
126 
124 
123 


corrosive  substances, 
hygrometric,       " 

Weights, 116 

adjustment  of,  ....  117 
divisions,  .  .  .  .  .117 
materials  for,  ,  .  .  .117 

testing  of, 118 

Weights  and  measures,  tables  of,  614,  617 
Wind  furnaces,  .  .  .  .219 
Wheel  barometer,  ....  387 
Weygandt's  galvanometer,  .  .  539 
Wire  for  batteries,  ....  557 
Wollaston's  battery,  .  .  .  549 
barometer,  ....  407 
Wolfie's  bottle,  .  .  .  .351 


Z. 


Zinc  for  batteries, 
local  action  in, 
amalgamating, 


548 
549 
549 


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